1. Diploma Thesis
University of Bonn
Institute of Computer Science II
Computer Graphics
Interaction Techniques for Immersive
Seismic Interpretation
Delger Lhamsuren
Supervisors:
Prof.Dr. Reinhard Klein
Dipl.-Inform. Stefan Rilling
August 14, 2014
2. STATEMENT OF ORIGINALITY
I hereby certify that I am the sole author of this Diploma thesis
Interaction Techniques for Immersive Seismic Interpretation and
that it represents my original work. I have used no other sources
except as noted by citations.
I also declare that all data, tables, gures and text citations which
have been reproduced from any other source, including the Internet,
have been explicitly acknowledged as such.
Delger Lhamsuren
1
3. ACKNOWLEDGEMENTS
First of all, I would like to thank Prof.Dr. Reinhard Klein from the University
of Bonn for supervising this thesis.
I would also like to thank my precious colleagues at the Fraunhofer IAIS. Special
thanks to my boss Dr. Manfred Bogen for reviewing my thesis and giving me
priceless life advice, my advisor Dipl.-Inform. Stefan Rilling for his constant
support and unrelenting guidance, M.Sc. Ömer Genç for the many great ideas,
my student colleagues Philipp Ladwig and Jannik Fiedler for making this an
enjoyable experience.
Furthermore, I would like to thank Dr. Hartwig von Hartmann and his col-
leagues at the Leibniz Institute for Applied Geophysics for sharing their exper-
tise with me and taking part in the user studies.
I want to thank my family and friends for always being there for me. Thanks,
Mom, Dad, Adega, for all your love and understanding. I have nally made
it. Thanks, Jean, Jenin, Franklin, Victor, Cristina, Rojan, Annette, Ilja, Krum
and Robert. Hope we'll be able to hang out more often now.
Thank you, Katharina, for everything, and I hope you don't mind if I put down
in words how wonderful life is while you're in the world.
2
5. 1 Introduction
This section provides an overview of the contents of this thesis by rst stating
the motivation for this thesis and then briey outlining each following section.
1.1 Motivation
In times of rising energy prices due to dwindling fossil fuel resources such as
coal, oil and gas, and increasing environmental problems associated with their
use, alternative energy sources are becoming more and more desirable. That
is where geothermal energy, the renewable energy source that derives from the
heat of the earth's core, comes in. It is greater along planar fractures and dis-
continuities in the earth's crust, making so-called fault zones viable sources of
alternative energy. The purpose of the research and development project Stör-
Tief [@ST], supported by the Federal Ministry for Economic Aairs and Energy,
is to provide a better understanding of the role these deep-seated fault zones
play in geothermal energy production. The Fraunhofer Institute for Intelligent
Analysis and Information Systems (IAIS), was entrusted with the work package
1.4 of this project. It is called The stereoscopic 3D visualization of seismic data
for the detection of deep-seated fault zones or SeisViz3D, in short [@SV3D].
As the title suggests, the goal is to build a stereoscopic 3D viewer of seismic data
that allows interaction with the data in ways that take advantage of the immer-
sive stereoscopic visualization. This can be roughly divided into the following
two main tasks: the 3D visualization of seismic data and the 3D interaction with
it. I was in charge of the latter. This thesis was written under the supervision
of Dipl.-Inform. Stefan Rilling from IAIS and Prof.Dr. Reinhard Klein from
the University of Bonn and presents the results of my endeavour.
1.2 Goals Of This Thesis
The goals of this thesis are to explore the possibilities of applying stereoscopic
3D, coupled with specially designed interaction techniques using a combination
of interaction devices, to seismic interpretation, specically to the interpreta-
tion of faults. In the process, a variety of interaction devices and techniques
were tested, rst to evaluate the usability and applicability of the devices on
their own, then to check in a nal study on the basis of an example seismic
interpretation task, whether the stereoscopic 3D together with said techniques
was able to improve the general seismic interpretation workow.
The main hypothesis of this thesis can be stated as follows:
Hypothesis 1 Stereoscopic 3D coupled with intuitive 3D interaction makes for
a more ecient seismic interpretation.
What a seismic interpretation workow entails and how the proposed interac-
tion techniques work in detail will be explained in sections 2 and 5, respectively.
4
6. 1.3 Outline
This thesis contains 8 sections.
1. The rst section is this introduction.
2. The section Geothermal Exploration provides the geothermal background
and explains why seismic interpretation plays a crucial role in the search
and extraction of geothermal energy.
3. The section Existing State-of-the-art Seismic Interpretation Systems presents
two widely used seismic interpretation systems and their approaches to
seismic interpretation to show the state of the art today.
4. The section State Of The Art In 3D Interaction gives a state-of-the-art
report too on the fundamentals of 3D interaction, the dierent input and
output devices, and the types of approaches to 3D interaction.
5. The section Proposed Interaction Techniques introduces the setup used in
this implementation, a pre-development user study regarding input de-
vices, and the two programs that were developed to demonstrate the pro-
posed interaction techniques in form of a typical seismic interpretation
workow.
6. The section Software Architecture takes a detailed look at the structure of
the two developed programs, their core components, and how they interact
with each other.
7. The section System evaluation describes the nal user study that was
conducted to evaluate the proposed interaction techniques and its results.
8. The section Conclusion Future Work summarizes the ndings of this
project and hints at how the techniques can be further improved to achieve
even better results.
5
7. 2 Geothermal Exploration
2.1 Geothermal Energy
The Maoris in New Zealand and Native Americans used water from
hot springs for cooking and medicinal purposes for thousands of
years. Ancient Greeks and Romans had geothermal heated spas. The
people of Pompeii, living too close to Mount Vesuvius, tapped hot wa-
ter from the earth to heat their buildings. Romans used geothermal
waters for treating eye and skin disease. The Japanese have enjoyed
geothermal spas for centuries. [Ner10]
As the term geothermal, coming from the Greek words geo (earth) and therme
(heat), suggests, heat has been radiating from the center of the earth for about
as long as our planet exists. The temperature close to the earth's core is around
5, 500 ◦
C Celsius, which is about as hot as the sun's surface. The heat transfers
to the surrounding layer of rock, the mantle, which eventually melts due to
the rising temperature and pressure, becoming magma. Since magma is less
dense than the surrounding rock, it rises, moving slowly up toward the earth's
crust. Sometimes it reaches all the way to the surface as lava, but most of
the time, magma remains below the surface, heating nearby rock and rainwater
that has seeped deep into the earth to a temperature of up to 370 ◦
C. This hot
geothermal water travels back up to the surface along ssures and faults in the
crusts. [@GEO]
There are records of hot springs being used for bathing since prehistoric
times [Cat93], with the oldest being of a spa in the form of a stone pool, built
in the Qin Dynasty in the 3rd century BC [ST14]. Other famous examples are
ancient Greeks erecting public health spas and sanitariums on natural springs,
where patients suering from various ailments could nd treatment [@GR], and
Romans emulating the Greeks' bathing practices, using hot water to heat public
baths and feed underoor heating. The baths were usually privately owned, but
were public in the sense that they were open to the populace for an admission
fee, making it the rst commercial use of geothermal power in the history of
mankind [@Cry]. However, it was not until the 20th century that this practi-
cally inexhaustible supply of energy was exploited industrially as an electricity
generating source.
As opposed to conventional power sources, especially fossil fuels like oil and
gas, which draw on nite resources that may eventually become too expensive to
retrieve, geothermal energy is a clean, renewable, and essentially limitless alter-
native. Even among the various renewable energy sources, geothermal energy is
special, as it is capable of producing constant power year-round. Compared to
solar and wind power, which are only available, when the sun has been shining
or the wind blowing, respectively, this is a signicant advantage.
On July 4, 1904, Prince Piero Ginori Conti successfully powered a few light
bulbs from a 10-kilowatt dynamo coupled with a steam engine, using only
geothermal energy on the dry steam elds of Larderello, Italia (See Figure 1).
6
8. Figure 1: Prince Piero Ginori Conti and his 15 kW geothermal steam engine on
July 4, 1904 [@UGI].
The success of the experiment led, in 1911, to the construction of the world's
rst commercial geothermal power plant there. The system had been improved
so much that it was able to generate 250 kW of electricity in 1913 [TG05]. Now,
more than a century after that, 24 countries in the world are using geothermal
power, while another 11 are developing the capacity to do so [@GEA]. Modern
geothermal power facilities have output capacities of hundreds of megawatts,
with the biggest being the Geysers Geothermal Complex located about 121 km
north of San Francisco, Califonia, with an active production capacity of 900
MW [@PT]. In 2010, the International Geothermal Association (IGA) reported
that a capacity of 10,715 MW is installed worldwide, capable of generating
67,246 gigawatt-hours of electricity [@GEA], but this amount is miniscule com-
pared to the total annual potential of 1,400,000 terawatt-hours [Joh+06], which
is more than 10 times the total worldwide energy consumption of 132,000 TWh
in 2008 [@BP]. This is proof that, despite the annual growth of three percent
over the last decade [Ber07], the potential of geothermal resources appears to be
severely under-realized, with the biggest part remaining undeveloped and largely
untapped in the vast majority of countries in the world, while many countries
have just started accessing their resources. This brings us to the question of
how to reliably locate and extract geothermal energy resources.
2.2 Geothermal Exploration
Geothermal Exploration is the subterranean exploration for viable active geo-
thermal resources, usually with the purpose of electricity generation by installing
7
9. a geothermal power plant. Hot spots for geothermal energy are characterized
by the following four geothermal elements [Man06] (See Figure 2):
1. Heat Source - Every geothermal region needs a source for its heat, e.g. a
high temperature magmatic body in relatively shallow depths (5-10 km).
2. Reservoir - The reservoir is a collection of hot permeable rocks from
which circulating geothermal uids extract heat. However, it is usually
overlain by a cover of impermeable rocks.
3. Geothermal Fluid - Geothermal uids are gas, vapor and water that
carry the heat from the heat source up to the surface.
4. Recharge Area - Reservoirs are connected to a surcial recharge area
through which meteoric waters, e.g. rain, can replace or partly replace
the uids that escape from the reservoir.
Figure 2: An ideal geothermal system that contains all four characteristics of a
hot spot [@IGA].
According to the Geothermal Handbook of Energy Sector Management As-
sistance Program (ESMAP), geothermal exploration is a seven-phase process
[@ESMAP]:
1. Preliminary survey - The Preliminary Survey phase involves a work
program to assess the already available evidence for geothermal potential
within a specic area.
8
10. 2. Exploration - The purpose of the Exploration phase is to analyze and
cost-eectively minimize risks related to resource temperature, depth, pro-
ductivity, and sustainability prior to test drilling.
3. Test drilling - The rst exploratory wells are drilled during this phase.
Typically, at least two, but more often three, deep wells are drilled to
demonstrate the feasibility of commercial production and injection.
4. Project review and planning - Once the resource has been discovered
and conrmed by the rst few test deep wells, an accurate feasibility report
is written, which permits the developer to update and rene its reservoir
model and plan the next steps.
5. Field development - The project now proceeds to the Field Development
Phase with the drilling of a sucient number of deep production and
reinjection wells to support the proposed power production.
6. Power plant construction - Along with further testing of the wells, the
power plant can be nally constructed.
7. Commissioning and operation - At this point, the power plant can be
taken into operation.
Figure 3: The project cost and risk prole at various stages of develop-
ment [@QG].
While drilling is the most accurate exploration method, it is also the most
expensive and risky one, with costs estimated at $400 per feet [Jen09]. Naturally,
you want to avoid unnecessary exploratory drills as much as possible to locate a
geothermal resource, making the Exploration and Test drilling phases the most
crucial for the success of the process (See Figure 3). Especially the analyses
9
11. in the Exploration phase prior to the rst drilling are important, as they can
signicantly increase the chances of a successful drilling. These less costly means
of exploration can be categorized as follows [Man06]:
1. Gravity methods - Magmatic bodies are generally less dense than its
host rock. Gravity surveys are employed to detect these anomalies.
2. Magnetotelluric methods - Geological materials have a high electri-
cal resistivity since they are generally poor electrical conductors, while
hydrothermal uids in the faults and fractures of the earth increase the
conductivity. Magnetotelluric surveys examine these resistivity anomalies.
3. Magnetic methods - Common magnetic minerals lose their magnetiza-
tion at about 580 ◦
C, the Curie temperature. Magnetic methods are able
to detect the depth of a crust with this temperature. Regions with shallow
Curie-temperature depths suggest a higher geothermal potential.
4. Seismic methods - Magmatic bodies and rocks near melting temper-
ature have an unusually slow seismic velocity. Seismic methods record
reections of seismic waves to either search for parts of the crust that ex-
hibit this anomaly, or produce a general three-dimensional image of the
seismic structure as a whole. The latter is called Seismic tomography.
In the case of natural waves, e.g. caused by earthquakes, seismic studies
are called passive, while active seismic studies require man-made waves,
usually caused by explosions, specialized air guns or seismic vibrators.
The described implementation will exclusively deal with data from seismic
surveys, also called seismic reection data.
2.3 Seismic Reection Data
Figure 4: Example seismic reection data [@VSA].
Seismic reection data, often referred to as seismic reection volumes, is
acquired by sending seismic waves, often sound waves from explosions, into
10
12. the earth and recording their echoes. When a wave hits the boundary of two
subsurface layers, a seismic horizon, it is partly transmitted to the lower layer
and partly reected back to the surface. Recording these reections over time
results in a set of 1D values for each time step, and arranging them in the form
of a grid in the XY-plane produces a timeline slice. Rearranging the sets of
traces along the X- and Y-axis with the same positions in the grid form the
inline and crossline slices, respectively (See Figure 4). Putting the three sets of
slices together results in a discrete three-dimensional data. By estimating the
sonic speed for each layer, one can convert the time axis to an actual spatial
dimension, and transform the volume into a depth-converted volume. This is
called time-depth conversion. One of the advantages of working with this kind
of data is that it allows visualizing all layers at once. The interpretation of this
type of data is referred to as seismic interpretation.
2.4 Seismic Interpretation
The general goal of seismic interpretation is to trace continuous subsurface struc-
tures throughout a seismic volume and ultimately create a 3D model of them.
The extraction of seismic horizons is an important example, since most other
structures are primarily dened by their interaction with horizons. Horizons are
easy to see, even for the untrained eye, as they are represented in the volume
by bands of locally extremal values. From here on, the extraction of seismic
horizons will be referred to as horizon picking.
Seismic interpretation, in general, is a time-consuming and error-prone task,
usually resulting in hours of manual work that needs to be repeated in case of an
error. This is mainly due to the workow of conventional seismic interpretation
systems being heavily based on 2D slices. It requires the interpreter to manually
or semi-automatically interpret every n-th inline and crossline slice of a seismic
volume, with n ranging from skipping several slices each step to processing each
slice one by one. To avoid going through the data slice by slice more than once,
the interpreter traces multiple horizons, or whatever is being modeled, on each
slice. Once all slices have been interpreted, the gaps inbetween, for which there
is no data available, are lled using automatic growing and surface interpola-
tion algorithms. The nal step is to build a geological 3D model out of the
extracted and interpolated points, using the aforementioned time-depth conver-
sion method. These extracted structures must t and correspond to additional
spatial data provided by other exploration means. If they do not, there must
have been errors during the interpretation, forcing the interpreter to go through
the data again to correct and rene the extracted points [Höl+11].
In this thesis, the primary focus lies on fault interpretation. Faults are planar
fractures or discontinuities in the Earth's crust. Not only are they responsible for
the circulation of geothermal uids beneath the surface, but they are often prime
drilling locations, as their densities are much less than surrounding material,
making them important targets of seismic interpretation [@EGS]. Picking a
fault technically works in a similar way as picking a horizon does, only in this
case, the interpreter traces the vertical gaps and interruptions of horizons on
11
13. each slice. While there are quite reliable automatic tracking algorithms for
horizons due to their nature of showing up as locally extremal values in the
data, automatically detecting faults is a far more complex task. As a result,
fault picking is almost entirely carried out manually.
To summarize, a typical seismic interpretation workow entails the following
basic steps:
1. Load and visualize seismic data in 2D or 3D.
2. Inspect data by navigating through it.
3. Locate structures of interest, such as horizons and faults.
4. Pick structures of interest by tracing it, point by point.
5. If picked points are not precise enough, repeat step 5.
6. Interpolate picked points into 3D models.
For the sake of simplicity, this workow will be referred to as seismic inter-
pretation workow throughout this thesis.
12
14. 3 Existing State-of-the-art Seismic Interpretation
Systems
In this section, existing state-of-the-art seismic interpretation systems will be
closely examined with the focus on their typical seismic interpretation workows.
There are, of course, many dierent seismic interpretation systems to choose
from, but for the sake of comparison, the following two widely used systems
were chosen: First, a commercial system called Petrel, the agship product
of Schlumberger, the world's largest oileld services company [@BLO], then
OpendTect, a free open-source system that is considered to be of commercial
quality by many.
3.1 Petrel
Petrel is an Exploration Production software platform that was originally
developed by a company called Technoguide in Norway, and later taken over
by Schlumberger, one of the leading suppliers of technology, integrated project
management, and information solutions to customers in the oil and gas industry.
It is meant to be a complete solution that oers a full seismic-to-simulation work-
ow, from seismic interpretation including modelling, project planning through
simulation, to production analysis on a single platform [@SCH1]. In 2010,
Schlumberger released the open-source Ocean software development framework
that makes it possible for third parties to integrate their specialized technologies
and workows directly into Petrel via plugins, and release them in the Ocean
Store, a specialized online store for Petrel plug-ins. As of July, 2014, there are
124 plug-ins available [@SCH2].
The following interface and seismic interpretation workows were taken from
the 2010 version of Petrel [@SCM].
3.1.1 Interface
As you can see in Figure 5, Petrel uses a typical WIMP interface with the
following structure:
ˆ Menu bar - Gives access to the following list of features:
File - File manipulation, opening, closing, etc.
Edit - File editing.
View - Settings related to what can be seen in the Display window.
Insert - Creation of new folders and objects.
Project - Settings related to the Petrel project and simulators.
Tools - Contains simulators and general Petrel tools.
Window - Creation and manipulation of graphics windows.
Help - Help for the Petrel application.
13
15. Figure 5: Screenshot of the Petrel user interface [@YOU1]
ˆ Toolbar - Tools for commonly accessed commands that can also be found
in the Menu bar.
ˆ Function bar - Process-specic tools that change with the selected Pro-
cess in the Process diagram.
ˆ Explorer panes - Petrel's le manager for all related model data comes
with the following eight panes:
Input - Imported data such as lines, points, gridded surfaces and
volumes is stored here. Output data of seismic interpretation, such
as generated fault polygons, is automatically put here as well.
Models - Internally created data connected with a 3D model, such
as faults, trends and 3D grids, is stored here. Imported models are
also put here.
Results - The numerical results of volume calculations and simula-
tions are stored in this pane.
Templates - Color tables for continuous, discrete and seismic prop-
erty templates etc. are stored under this pane.
14
16. Processes - Contains the list of available processes in Petrel.
Cases - Contains the actual cases related to simulation and volumet-
rics results.
Workow - Stores results from the Workow editor and Uncertainty
and Optimization process.
Windows - Stores all opened and active plots and windows used in
the Petrel project.
ˆ Display window - Checked items in the Explorer panes will be displayed
in the active Display window. Depending on the data, it can be a 2D or
3D viewer.
3.1.2 Seismic Interpretation Workow
This is how a typical seismic interpretation workow looks like in Petrel:
1. Import data - First of all, you need to import the data you want to
interpret. Among others, Petrel can import seismic 2D lines and 3D cubes
in SEG-Y and ZGY format.
2. Visualize Data - Right click on an imported seismic line in the Input
pane and choose Create Interpretation Window to get a classic 2D view
of the data in the Display Window.
3. Commence Seismic Interpretation - Click on the Seismic interpre-
tation process to enable the Interpretation tools in the toolbar.
4. Pick Horizons - Activate the Interpret grid horizons icon in the
Function bar to perform a horizon interpretation of any kind. Right-click
on an interpretation folder and select Insert seismic horizon to create
a new horizon. Then choose one of the following options to start picking
a horizon:
Figure 6: Left: Manually selected seed points in the 2D view; Right: Automat-
ically generated 3D horizon with the Seeded 3D autotracking option [@YOU1].
15
17. ˆ Seeded 3D autotracking - Points will be tracked outwards from
a number of manually selected seed points in all directions. This
method can be very ecient when the reectors are of good quality
(See Figure 6).
ˆ Seeded 2D autotracking - Points will be tracked in the direction
of the selected line intersection.
ˆ Guided autotracking - You select two points and the tracking tries
to nd the best route from one to the other. This gives you a high
degree of control as to how the interpretation will develop.
ˆ Manual interpretation - You select all points of the horizon man-
ually.
5. Pick Faults
(a) Activate the Fault Interpretation icon in the Function bar.
(b) Right click on an interpretation folder and select Insert New Fault
to create a new fault.
(c) Start interpreting by picking points that belong to a fault. A rubber
band display connecting the last selected point and the location of
the cursor will be seen, aiding the interpreter to set the next fault
point.
(d) Once you are nished tracing a fault on a slice, press the N or F key
to end the current fault segment and begin a new one on the next
slice.
(e) Repeat the process(See Figure 7).
Figure 7: Left: Manually selected Fault points in the 2D view; Middle: Auto-
matically generated Fault sticks from the side; Right: Automatically generated
Fault sticks from above [@YOU2].
16
18. 3.2 OpendTect
OpendTect is a full-featured seismic interpretation platform built by dGB Earth
Sciences, a privately owned software and service company that provides seismic
interpretation solutions to the oil and gas industry. The base tool with its
essential functionalities to process, visualize and interpret seismic data is free
and open source, but can be optionally extended with many commercial, closed-
source plugins [@ODT].
3.2.1 Interface
As you can see in Figure 8, OpendTect too uses a typical WIMP interface
comprised of the following elements [@OUD]:
ˆ Main menu bar - Gives access to the following list of modules:
Survey - This menu is used to select, create, modify, delete or copy
surveys (projects). It also lets you import and export data.
Analysis - This menu contains a variety of analysis tools that can
be dened, such as Attributes (quantities extracted or derived from
seismic data) and volume-based tools.
Processing - From this menu, the user can trigger the actual pro-
cessing of the analysis tools that were dened in the Analysis menu.
Scenes - This menu lets the user manage multiple scenes, each scene
with its own tree. Scenes behave like sub-windows within the main
window.
View - The user can modify the work area to their needs and toggle
on/o stereo viewing.
Utilities - In this menu, the user can change applications settings,
such as controls and appearance, and manage tools and plugins.
Help - The user can access a help documentation from this menu.
ˆ Toolbars - OpendTect contains a number of toolbars:
OpendTect toolbar - Contains OpendTect-specic analysis mod-
ules.
Manage toolbar - Contains shortcuts to managers of seismic data.
Graphics toolbar - Contains settings regarding the appearance of
the scene.
Tracking toolbar - Contains tools that control the picking of hori-
zons.
Slice position toolbar - Is used to position the slices in the 3D
scene.
ˆ Tree scene control - A tree view of each scene consisting of several
elements of dierent types, such as slices, volume, horizons, faults, etc.
17
19. Figure 8: Screenshot of the OpendTect user interface [@OdTS]
ˆ 3D scene - Shows the selected scene with all its elements in 3D. Opend-
Tect also oers a 2D viewer for slices.
18
20. 3.2.2 Seismic Interpretation Workow
The following depicts a typical seismic interpretation workow in OpendTect:
1. Import Data - The rst step in OpendTect is always to dene a new
survey (project) and import seismic data. The data must be in SEG-Y
format.
2. Visualize Data - Next, right-click on inline/crossline in the Tree
scene control and choose Add to display an inline/crossline from the loaded
data in the 3D scene.
3. Add A New Horizon - Click on Horizon in the tree and select New....
This will open a tracking setup dialog with tracking options.
4. Dene Tracking Mode - Choose one of the following tracking modes:
ˆ Tracking in volume - Auto-track a horizon inside a tracking area
(3D subvolume) that can be moved and adjusted during interpreta-
tion. This is the preferred mode for most seismic data.
ˆ Line tracking - Auto-track a horizon on a slice (inline or crossline)
in the 2D viewer, giving the interpreter more control for areas where
the Tracking in volume mode fails.
ˆ Line manual - Manually pick a horizon on a slice in the 2D viewer.
For areas where both auto-tracking modes fail.
Figure 9: (1) Manually selected seed points and the surrounding tracking
area [@ODT1]; (2) Automatically generated 3D horizon within the tracking
area with the Tracking in volume option [@ODT2]; (3) Tracking area moved to
next position [@ODT3]; (4) Horizon is auto-tracked at new position [@ODT4].
5. Pick Horizons - Start picking a horizon in the tracking mode of your
choice:
ˆ Tracking in volume
(a) Pick seed points by clicking on a slice in the volume.
19
21. Figure 10: Horizon picking with the Line tracking or Line manual mode in the
2D viewer [@OdTH].
(b) Optionally, display the tracking area cube and resize it by drag-
ging the green anchors on the edges.
(c) Once everything is ready, click the auto-track icon to automati-
cally extract a 3D horizon out of the data.
(d) Then move the tracking area cube to the next position by clicking
the top of the cube and dragging it. Note that a small part of
the already extracted horizon should be inside the new position
of the cube.
(e) Click the auto-track icon again to auto-track the horizon at the
new position.
(f) Return to step (d) and repeat the process (See Figure 9).
ˆ Line tracking and line manual
(a) Right-click on the seismic data in the tree and select Display
2D Viewer.
(b) Select the track/edit mode button and pick seed points on the
displayed slice.
(c) Move the resulting line until it ts.
(d) Repeat the process (See Figure 10).
20
22. Figure 11: Three fault sticks picked on an inline slice in OpendTect [@OdTF].
6. Pick Faults
(a) Click on Fault in the tree an select New to create a new fault.
(b) Pick points by clicking on a slice in the scene that belong to a fault.
The fault model is displayed as an ordered sequence of fault sticks.
(c) Once you are nished tracking a fault on a slice, right-click on the
fault and select Save.
(d) In the Save dialog, name the fault and press OK to save and update
the name of the interpreted fault.
(e) Continue the fault picking on a dierent inline/crossline by scrolling
to a dierent slice using the Slice position toolbar.
(f) Repeat the process (See Figure 11).
3.3 Conclusion
Despite their vast amount of powerful seismic interpretation funtionalities and
algorithms, the actual seismic interpretation workows of the two introduced
solutions are both based on conventional 2D interaction using 2D input devices
on 2D slices of the 3D data. In general, the interpreter activates a certain
interpretation mode from the 2D graphical user interface, then scrolls through
the data, slice by slice, to pick points on the slices. This can be done manually
or with the assistance of an autotracking algorithmm, which are then converted
into 3D models. Both systems oer stereoscopic 3D, but neither the workow
nor the visualization is optimized to it in any way. The only supported input
21
23. devices are traditional 2D pointing devices, such as mice and tablets. According
to the main hypothesis of this thesis, this is simply not enough.
22
24. 4 State Of The Art In 3D Interaction
Before any kind of 3D interaction technique can be developed, it is important
to return to the basics and take a closer look at 3D interaction in general, with
its advantages and disadvantages, stengths and diculties.
4.1 Introduction
Ever since Windows, Icons, Menus, Pointing device (WIMP) interaction was
developed by Xerox in 1973, popularized by Apple's Macintosh in 1984 [Dam97],
and turned into the standard with Microsoft Windows 95 [@UH], graphical user
interfaces (GUIs) do not seem to have changed much at all in the last 30 years.
Even Windows 8, the latest version of Windows, with its new Metro interface
only appears dierent at a rst glance, until you nd yourself using the desk-
top app with the classic WIMP environment most of the time. Nevertheless,
Microsoft's decision to change their successful formula, even if not completely,
proves that user interaction, as we know it, is nally undergoing a change.
Since the huge success of the iPhone in 2007, devices with multi-touch interac-
tion like smartphones, tablet PCs, laptops with touchscreens, and standalone
touchscreen monitors have become ubiquitous. But even though Apple claims
to have invented multi-touch for the iPhone [@BI], the technology dates back
to the early 80's [Meh82]. Even some of Apple's famous patented gestures,
such as pinch-and-zoom, had been used decades before they found wide-spread
use [KGH85]. So if both the technology and the interaction was already there,
why did it take so long for multi-touch to achieve its breakthrough? The mouse
is yet another example for this phenomenon. Although it was invented by Dou-
glas Engelbart in 1964 [@DEI], it was not until 20 years later that the mouse
became the dominant pointing device for WIMP interaction [@MHP]. It seems,
for a new technology to be successful, the following conditions must be met:
1. The technology must be potentially useful.
As with the mouse and multi-touch, this is necessary, but not sucient.
2. The technology must be aordable.
In the end, the price might be the deciding factor for a certain product,
but a too high price has rarely stopped a new trend, it can merely slow it
down temporarily.
3. The industry and, with it the target group, must be ready for the new
technology.
The last condition may be the most important one. In the case of multi-
touch, for instance, the industry was reluctant to change the WIMP interaction
paradigm and worked on better mice and mouse replacements like pen tablets
instead, until smartphones popularized touch interaction. It should be noted
that it is probably futile to try to completely replace the mouse in the rst place,
without changing the way of interaction rst. The mouse is perfect for certain
23
25. tasks, so it is wiser to try to nd new devices that complement the mouse, or
replace it only for cases where the mouse is rather lacking [@BB]. One such
case is 3D applications with 3D interaction. The mouse was just not designed
to work in 3D. The 3D mouse was, but simply adapting the traditional WIMP
interaction paradigm along with its devices to 3D can not be an optimal solution
to this problem. And this brings us back to the conditions that must be met
for the success of a new technology.
1. The technology must be potentially useful.
Research on 3D interaction can be traced back to 1968, when Dr. Ivan
Sutherland created the rst Computer-Aided Design (CAD) tool, which
allowed the sketching of 2D and 3D graphics directly on the computer
screen [@DW]. Since then, countless 3D input and output devices have
been developed. 3D input devices include motion trackers, 3D pointing
devices, and whole-hand devices allowing gestural input. Examples for 3D
output devices are stereoscopic displays, head-mounted displays, spatial
audio systems, and haptic devices. Each of the devices have proven that
they are useful in their own right.
2. The technology must be aordable.
Admittedly, this was a big problem with 3D devices for a long time. But
with the recent success of motion-control devices like the Nintendo Wii,
Xbox360 Kinect, and the Playstation Move, new input devices are sold on
the market at a relatively cheap price [Juh13], e.g. the Leap Motion, a
ne-tuned 3D motion control device for up to 10 ngers at once. Thanks to
the inux of 3D HDTV's in living rooms [@ZDN] and glasses-free 3D tech-
nology around the corner [@Y3D], stereoscopic visualization has returned
to the center of attention and prices have been sinking dramatically.
3. The industry and, with it the target group, must be ready for the new tech-
nology.
As long as the main operating systems only support 2D graphical inter-
faces, 3D interaction will never fully replace its 2D counterpart, but 3D
applications are a dierent story. People often have great diculties un-
derstanding 3D spaces and interacting with a virtual 3D world. Although
the world we live in is equally 3D, the physical world oers so many cues
and feedback that we are able to interact with it almost eortlessly. 3D
applications, including seismic interpretation software, are in dire need
of novel 3D interaction user interfaces and techniques, that are possibly
based on real-world interaction and feel natural to the user [Bow+01].
Since the obvious conditions for a successful integration of 3D interaction
seem to have been met, 3D interaction just might be the next big thing after
WIMP and multi-touch.
24
26. 4.2 Input Devices
There is a wide range of input devices available on the market. You can nd
anything, from classic 2D devices like keyboards and mice to newer devices like
smartphones and motion-control devices. Input devices can be roughly divided
into two groups, the lower-dimensional input devices and the higher-dimensional
input devices.
4.2.1 Lower-Dimensional Input Devices
Figure 12: Examples of lower-dimensional input devices: (1) Keyboard [@KKM]
(2) Trackball [@SG] (3) Touchpad [@TP] (4) Tablet [@ISO].
Lower-dimensional input devices only oer up to two Degrees of Freedom in
their input. Here is an overview of lower-dimensional input device types:
ˆ Keyboards
ˆ 2D Mice and Trackballs
ˆ Tablets
Lower-dimensional input is more than enough for what it was designed for,
namely 2D operating systems with 2D applications. For 3D applications, how-
ever, this is rather lacking, but it would not be wise to rule them out because
of this. In fact, classic 2D devices like mice are still widely used in 3D appli-
cations by simply mapping their 2D input into 3D operations. What makes
lower-dimensional input devices a valid choice for 3D applications is that they
are usually very cheap, ergonomic and simple to use. Their biggest advantage,
however, is that most users are already familiar with them. Ever since the break-
through of personal computers and WIMP user interfaces in the early 1980s,
using a mouse and keyboard has been the prevalent way of operating a com-
puter. The only notable new interaction methods that have seen widespread use
in recent years are pen- and touch-based input. Pen tablets are predominantly
used by graphic designers, although some tablets are intended as a replacement
for the mouse as the primary pointing device for desktop computers. On the
other hand, touch-based input has spread like wildre recently thanks to the
inux of touch-based devices, such as smartphones and tablet computers. The
disadvantage of using lower-dimensional input devices in higher-dimensional ap-
plications, however, is that it forces a user to use them in a way they were not
originally designed for. In other words, users have to mentally translate their
25
27. 2D actions into the 3D operations they were mapped into every time before they
perform an action [Tea08]. You do not nd this articial overhead in the case of
higher-dimensional devices that were specically designed for 3D applications.
Conventional seismic interpretation workows always involve a keyboard and
a mouse, which is why any seismic interpretation system should at least support
these two devices. Additionally, we considered a Wacom Cintiq Companion
tablet due to its versatility, with its pen and touch input and its built-in display.
4.2.2 Higher-Dimensional Input Devices
Figure 13: Examples of higher-dimensional input devices: (1) 3D Mouse [@ENG]
(2) CyberGlove [@GOL] (3) Wii remote [@BTF] (4) Kinect [@KIN].
Higher-dimensional input devices, also called 3D input devices, oer up to
six Degrees of Freedom, three translational and three rotational, and can be
broken up into the following categories [Bow+04]:
ˆ Tracking Devices
Motion trackers
Eye trackers
Data gloves
ˆ 3D Mice
ˆ Special-purpose Input Devices
ˆ Direct Human Input
Speech Input
Bioelectric Input
Brain Input
3D input devices are supposed to allow users to interact with 3D interfaces
and 3D scenes just like how you can use 2D devices with 2D interfaces. 3D mice,
for instance, can be seen as a simple extension of the idea of a 2D mouse. But
what seems simple in theory proves problematic in reality, as the addition of a
whole new axis of movement makes, what is already dicult to learn for novice
users in only two dimensions, several times more dicult, even for expert users
that are not familiar with the devices and their interaction techniques [Tea08].
26
28. As conventional seismic interpretation workows do not use 3D input de-
vices, we could freely choose from the variety of devices available on the market
and decided to use the 3D mouse 3Dconnexion SpaceNavigator as the 3D alter-
native to the mouse and the Leap Motion as a 3D motion tracking device.
4.3 Output Devices
In the context of interaction, output usually stands for feedback. Although the
most common type of feedback is visual, depending on the application, auditory,
haptic, tactile and olfactory feedback can be very important too. Output devices
can therefore be categorized according to their feedback as follows:
1. 3D graphics - All visual displays
2. Stereo viewing - 3D displays
3. Immersion - Head-mounted displays, caves
4. Nonvisual information - Auditory (e.g. 3D spatial sound systems),
tactile, and haptic displays
In the context of seismic interpretation, when an interpreter is working with
seismic data, s/he needs visual feedback, rst and foremost. Any other form of
feedback can be interesting, but currently there is no known seismic workow
that incorporates non-visual feedback. Hence, only visual displays are consid-
ered. Since they come in dierent sizes and shapes to suit every purpose, two
important criteria for visual displays must be dened [Bow+04]:
ˆ Field of Regard - Refers to the amount of the display space surrounding
the user, measured in degrees of visual angle.
ˆ Field of View - Refers to the maximum number of degrees, again mea-
sured in degrees of visual angle, that can be displayed to the user at once.
The FOV varies with the user's distance from the screen and must be less
than or equal to the maximum FOV of the human visual system (approx.
200 degrees) and will be lower if additional optics, such as stereo glasses,
are used.
Since immersiveness is the main goal of the SeisViz3D project, visual displays
were categorized according to the immersiveness they oer [Bow+01]:
1. Fully-immersive displays have a Field of Regard of 360 degrees in ev-
ery direction, occluding the real world entirely. This requires users to
be able to interact with the input devices blindly, since they cannot see
them. Examples for fully-immersive displays are head-mounted displays,
and virtual retinal displays. Since seismic interpreters have to be able to
work for extended periods of time, this type of displays are out of the
question for ergonomic reasons.
27
29. 2. Semi-immersive displays allow a user to see both the physical and vir-
tual world. Normal computer displays fall under this category. Physical
objects including a user's hands can obstruct a user's view, break the im-
mersion and, in case of a 3D display, disrupt the stereo eect. Interaction
techniques that require a user to move his/her hands or input devices
between their eyes and the display should be avoided.
Here are a few more important factors to consider when choosing a visual
display [Bow+04]:
ˆ Spatial Resolution aects how sharp text or images appear on the
screen, which can be crucial for immersion, and is often given in dots
per inch (dpi), but to be correct, dpi is a measurement that refers to the
dot density of a computer printer. Since displays have pixels rather than
dots, one should use pixels per inch (ppi), the pixel density, instead. To
compute the pixel density, you divide the width (or height) of the display
area in pixels by the width (or height) of the display area in inches. A
display's horizontal and vertical ppi can dier according to its ratio, which
is rarely 1:1.
ˆ Screen Geometry refers to the shape of a visual display. Visual dis-
plays come in all kinds of dierent shapes, incl. rectangular, L-shaped,
hemispherical, and hybrids. Nonrectangular screen shapes require non-
standard projection algorithms and can suer from visual artifacts such
as distortion.
ˆ Refresh Rate stands for the speed with which the displayed image on
a visual display is refreshed from the frame buer (usually in hertz, Hz,
refreshes per second). Note, however, that a higher refresh rate does not
mean that you will automatically have a higher frame rate and vice versa.
Even if an application wrote images into the frame buer at a higher rate
than the refresh rate, the visual display can show them only at its refresh
rate. Low refresh rates can be the cause for ickering.
3D functionality, a suciently high eld of view and resolution are essential
for the immersiveness the SeisViz3D project requires. Under the constraints of
the project, the choice fell on 3D Full HD displays with at least 55-inch screens.
4.4 Depth Cues
The primary dierence between a 2D and a 3D application is the addition of
a third dimension, commonly referred to as the depth. In 3D interaction, it
is crucial that users correctly perceive the distance of an object in a 3D scene.
Much like in the real world, this is accomplished by a number of depth cues that
help users interact with the scene, especially when performing 3D navigation,
selection, and manipulation tasks. Visual depth cues can be broken up into
three categories:
28
30. 4.4.1 Oculomotor Cues
Oculomotor cues are based on our ability to sense the position of our eyes and
the tension in our eye muscles [Gol02].
ˆ Convergence
When we look at an object in front of us, we stretch our extraocular
muscles to move our eyes inward, so their focus converges at the position
of the object. The kinesthetic feedback from this movement can help in
depth perception. The angle of convergence is bigger, when the object is
closer to the eye.
ˆ Accommodation
Accommodation refers to the sensation we feel when we contract and relax
our ciliary muscles to focus on far away objects. The ciliary muscles can
change the shape of the lens within the eyes, and with it, the focal length.
4.4.2 Monocular Cues
Monocular cues, also called static cues, refer to the depth information that can
be inferred from a static image viewed by a single eye:
ˆ Relative size
The further away an object is compared to an object of the same kind,
the smaller it appears to the viewer (See Figure 14).
ˆ Elevation
Objects tend to appear farther away for the viewer the closer they are to
the horizon (See Figure 14).
Figure 14: Relative size and elevation as depth cues.
ˆ Occlusion
Occlusion happens when an opaque object closer to the viewer partially
obstructs the view of an object farther away (See Figure 15).
ˆ Linear perspective
Parallel lines appear to converge as they move away from the viewer. The
farther the lines are from the viewer, the closer they appear to be to one
another (See Figure 16).
29
31. Figure 15: Occlusion as a depth cue.
Figure 16: Linear and aerial perspective as depth cues.
ˆ Aerial perspective
Due to scattering and absorption of light through the atmosphere, distant
objects appear to be dimmer and duller, while a closer object will have
more contrast and color saturation.
ˆ Lighting
Brighter and better-lit objects tend to appear closer to the viewer than
darker objects.
ˆ Shadows
The way an object's shadow is cast on adjacent surface or on other objects
conveys their position in space (See Figure 17).
Figure 17: Shadows as a depth cue.
ˆ Texture gradients
The density of patterns and details on the surface of an object appear to
increase with the distance between the object and the viewer.
ˆ Motion parallax
This dynamic depth cue is caused by objects moving past the viewer
30
32. (stationary-viewer motion parallax) or the viewer moving past objects
(moving-viewer motion parallax) or a combination thereof. Objects closer
to the viewer appear to move more quickly across the visual eld than
objects farther away.
4.4.3 Binocular Cues
Binocular cues are cues inferred from viewing a scene with both eyes.
ˆ Binocular disparity
Binocular disparity stands for the dierences between the two images the
viewer's eyes perceive due to their horizontal separation parallax. The
closer an objects is to the viewer, the more pronounced these dierences
are [Qia97].
ˆ Stereopsis
The two slightly dierent images from the eyes are converged into one
stereoscopic image and provide the viewer with an important depth cue
called stereopsis. In the rare case that the two images are too dierent
to be superimposed, e.g. when the object is too close to the eyes, the
viewer experiences a binocular rivalry, causing them to see the two images
alternatingly, one at a time, each for a randomly long time [HR95].
The signicance of a visual depth cue can vary depending on the circum-
stances. Stereopsis and convergence, for instance, are only helpful when the
viewer is within a 10-meter distance, since the binocular disparity decreases
with distance. Accomodation is only eective within a two-meter distance. In
contrast, motion parallax and occlusion are strong visual cues, regardless of the
viewer's distance to the objects [@HIT].
The question now is: Which of these depth cues can be synthetically gen-
erated in a 3D application? The monocular depth cues can and should be
generated with almost any visual display device, with most of them being a
result of correct 3D rendering. The same goes for motion parallax cues, as
it is automatically generated when the viewer and/or objects move through
the world. Stereopsis, however, can require special-purpose visual display de-
vices depending on the type of stereoscopy used, and the render software must
produce a dierent image for each eye with a geometrically correct binocular
disparity depending on the distance of the object [Bow+04].
As for oculomotor cues, stereoscopic visual displays automatically provide
proper convergence cues. However, stereoscopic displays are generally not able
to generate accommodation cues, because they create an articial environment,
where the intrinsic coupling between accommodation and convergence gets lost.
In Figure 18, a viewer is depicted looking at a conventional 2D display. The
viewer's eyes are marked by the points N1 and N2, while FP is the xation
point on the 2D display, at which the viewer's eyes converge. In this scenario,
the convergence angle θ1 matches the focal lengths N1 −FP and N2 −FP for the
left and right eye, respectively. Let us now look at the right side of the gure,
31
33. which depicts the same situation only with a 3D display. In this case, the display
shows two dierent pictures at every frame, one for each eye. Due to the virtual
binocular disparity that is created by the two pictures, the viewer's visual system
produces a virtual 3D image at position V and the viewer's eyes converge at
this point. This time, the convergence angle is θ2, but the focal lengths are not
N1 − V and N2 − V , as it should be, but N1 − FP1 and N1 − FP2, respectively.
This is due to the virtual 3D image being produced at a certain distance in front
of the display, while the real pictures are still rendered on the surface of the 3D
display. In other words, the user must focus at the screen to see the pictures
sharply, but the pictures are drawn in a way that the virtual object is popping
out of the screen. As a result, the user's oculomotor system sends conicting
signals to the brain about the distance to the object. Autostereoscopic devices
do not have this cue conict [Kim11].
Figure 18: Relation between the xation points, vergence angle and images
when a viewer watches (a) a 2D display or (b) a generic 3D display [Kim11].
4.4.4 Stereoscopic Viewing
In general, stereopsis can be generated with the help of a standard display and
some additional hardware, usually a pair of stereo glasses and a stereo-capable
graphics card. Autostereoscopic displays, on the other hand, do not need any
special hardware. Since a display has to show two images, one for each eye,
every frame, essentially halving the display's natural refresh rate, a high refresh
rate, at least 100 Hz, is necessary for an acceptable stereo quality. The purpose
of the glasses is to separate the two images for each eye to make sure that the left
and right eye only see the image that is rendered for them on the screen. Stereo
32
34. glasses can be either active or passive (See Figure 19). Active stereo glasses,
often referred to as shutter glasses, operate in sync with the visual display by
opening and closing their shutters with the refresh rate of the visual display,
i.e. enabling and blocking each eye's view in a coordinated sequence. This
approach is called temporal multiplexing. As the synchronization is usually
done with infrared signals, one should make it a general design rule to prevent
the user from moving his hands or other physical objects into the line of sight
of the glasses and emitters [Bow+04].
In the case of passive stereo glasses, polarization or spectral multiplexing is
used [SC02].
1. Polarization multiplexing polarizes the stereo images in perpendicular
directions before projecting them onto the screen, while polarizer glasses
with the same polarization lters lter out the right image for each eye.
2. Spectral multiplexing displays the left- and right-eye images in dierent
colors, usually complementary colors, e.g. red-green or blue-red, and the
viewer wears glasses with lters for the corresponding colors. This is also
called anaglyphic stereo, and is relatively inexpensive to produce, but lter
colors can not be used anywhere else in the application.
Figure 19: Left: Passive spectral glasses; Middle: Passive polarizer glasses;
Right: Active shutter glasses [@3DV].
To summarize, active stereo allows the highest stereo quality, while passive
stereo is the cheapest and simplest method, with inexpensive glasses and the
lack of synchronization issues.
4.5 Interaction Techniques
This subsection will introduce dierent approaches to implementing the most
important 3D interaction tasks: Navigation, Selection, Manipulation, and Sys-
tem Control.
4.5.1 Navigation
The visualization of seismic data results in large-scale 3D environments, so users
will inevitably spend most of their time navigating through the 3D scene. Hence,
the application must always give users sucient clues for the current position
inside the data, and provide an ecient and eortless way of moving from one
place to another. In other words, navigation is the most basic interaction task
33
35. and therefore must be so simple and easy that users are able to focus on more
complex tasks at all times.
In general, all navigation tasks belong to one of the following three cate-
gories [Bow+01]:
1. Exploration - When a user is exploring, s/he is navigating through the
scene and investigating the data without a specic target.
2. Search - In this case, the user wants to move to a certain target location.
3. Maneuvering - This category usually consists of small movements like
ne adjustments of the viewpoint, when the user has already reached the
target location.
Each of these types of tasks may require dierent interaction techniques. But
in general, any type of navigation is solved by using a metaphor. Let us take a
look at ve widespread metaphors for travel interaction techniques [HS14]:
1. Physical movement involves the user actually moving their body in a
way they normally would to travel through the virtual scene, e.g. walking
around in a wide-area motion tracking system, walking in place, on a
treadmill or riding a stationary bicycle. While such interaction techniques
can feel natural, they are not very precise, but all the more physically
tiring.
2. Manual viewpoint manipulation allows the user to specify the new
viewpoint by using hand motions. Examples are the camera in hand
metaphor, where the user's hand motion species the position of the cam-
era, and the scene in hand metaphor, in which the scene itself or an
object in the scene is attached to the user's hand. These techniques can
be easy to learn and ecient for short-time use, but since they require the
user to move his whole hand, they can be rather tiring too.
3. Steering techniques let the user fully control the direction of motion.
Continuous steering takes the orientation of either the user's head as the
direction of travel, as it is the case with gaze-directed techniques, or the
user's hands like in pointing techniques. It should be noted that a compar-
ison of steering techniques in 1997 showed a pointing technique to be much
more ecient than a gaze-directed one. Apparently, it was because gaze-
directed steering forces the user to always look in the direction of motion,
while pointing allows the user to look at the object of interest while mov-
ing. As opposed to continuous steering techniques, discrete steering uses
discrete commands, e.g. in a speech-recognition technique, where the user
can issue verbal commands to control the direction. Steering techniques
are very good in terms of eciency and ease of use.
4. Target-based techniques are completely opposite to steering techniques
as far as Degrees of Freedom is concerned, as they only allow the user
34
36. to specify a target from a set of targets and the system takes care of the
actual movement. The target location can be reached immediately after a
target has been selected, or the system may carry out a transitional move-
ment between the current location and the target location. Obviously, the
selection of the target requires a selection technique.
5. Route planning resembles target-based techniques in how the system
handles the movement, but the path of movement must be specied by
the user. This may be implemented by drawing a continuous route for the
system to follow or placing a set of markers, while the system interpolates
a path between the marker points. The advantage of these techniques is
that the user can plan the route ahead and can perform other tasks during
its execution.
The proposed interaction techniques make use of Steering and Target-based
techniques to navigate through the seismic data.
4.5.2 Selection and Manipulation
Once the user has navigated to the object of interest, they will want to select
the object, and manipulate it, e.g. by positioning or rotating it. The biggest
issue herein is again the choice of an appropriate manipulation metaphor that
makes it possible for users to manipulate virtual objects as easily as they can
manipulate real objects. The history of 3D interaction could be described as
the search for appropriate interaction metaphors. Here are some prominent
metaphors [@UCL]:
ˆ The Virtual Hand metaphor is based on the idea that we use our hands
in order to interact with objects in real life. The user can select virtual
objects by touching them with a virtual hand, which follows the movement
of the user's physical hand. Once the user has selected an object, it is
attached to the virtual hand to simulate holding an object and the object
can be manipulated with other hand gestures. Cybergloves utilized this
metaphor. While this metaphor is intuitive, it only allows objects within
one's short area of reach to be picked up.
ˆ The Go-Go metaphor allows the user to extend the virtual hand farther
than the natural reach. When the user's hand passes a certain threshold
distance, the mapping between the virtual hand and the user's hand be-
comes non-linear and the user's virtual arm begins to grow according to
a polynomial function.
ˆ The Ray Casting metaphor is about selecting an object in a 3D scene by
pointing to it with a virtual ray. The direction of the ray can be derived
from the position and orientation of the user's hand or a tracked wand.
Upon selection, the virtual object is attached to the tip of the ray and
can be manipulated. The Space Wand and the Wii Remote are example
applications of this metaphor.
35
37. ˆ HOMER (Hand centered Object Manipulation Extending Ray
casting) is a combination of the above three metaphors. The user uses
Ray Casting to select an object, but uses the Virtual Hand metaphor to
manipulate it. This could be realized with a combination of glove and
wand interaction devices or with motion sensing devices such as the Leap
Motion or Kinect.
As a general rule, it is important to implement constraints on an interaction
task and limit its degrees of freedom whenever possible to make it as simple as
possible.
In my implementation, an interaction metaphor similar to the HOMER
metaphor is used.
4.5.3 System Control
System control commands either modify the state of the system or the mode
of interaction, and as such, require the user to select an element from a set.
Therefore, system control tasks can be seen as an application of a selection
task. The conventional way of system control in form of pull-down menus and
command-line input is often not a viable option in a 3D application, since most
good old interface paradigms are not as ecient in 3D anymore. For instance,
selecting an item from a 3D menu oating in space is a much more dicult task
than selecting a 2D menu item in a 2D interface, not only due to the addition
of a third dimension, but also because the user will most probably be using a
dierent input device than a 2D mouse to perform the task.
Ideally, a system should not use any modes at all, since any kind of mode
change during an interaction task will disturb its ow of action. Another advan-
tage of a modeless interaction is that the controls for interaction stay the same
throughout the application. The user can interact with the same set of actions
regardless of which state or mode the system is in, which helps the user focus
on the task. Naturally, a complex program is bound to have more than one
mode. One way of simplifying system control tasks is to place the interface in
a xed position that is easily accessible for the user. This is not only applicable
to graphical menus, but also tools. The goal is to design an interface that can
be operated almost blindly. Appropriate feedback to notify the user of which
mode is currently active is crucial in preventing mode errors, as the application
not doing what the user expects it to because it is still stuck in a dierent mode
can be a very irritating experience [T00].
System control techniques in immersive 3D applications can be categorized
into the following four groups, each with their own advantages and disadvan-
tages [Bow+01]:
1. Interaction with a 2D/3D graphical user interface
Pros: Users are familiar with the concept and, if designed well, menus are
as simple as a 1D task and can be as complex as theoretically needed.
Cons: Menus take up a lot of space, as they must be big enough to allow
36
38. stable input with the rather imprecise 3D input devices. 2D GUIs can
break immersion.
2. Voice interaction
Pros: The microphone is a simple-to-use input device that allows the user
to use their hands for other operations, and voice input is exible enough
to allow complex commands.
Cons: Voice recognition is far from perfect, and voice commands have to
be quite long to be stably recognized. The user has to memorize all the
dierent commands, and a quiet environment is needed.
3. Gestural interaction
Pros: The human hand is exible and oers a great number of degrees of
freedom, eliminating the need for a traditional input device.
Cons: Recognition rates are still rather poor, and the user has to remem-
ber new gestures, as there are no standard hand gestures yet. For these
reasons, most 3D applications only make use of menus and/or buttons,
with only a few primitive gesture commands.
4. Tool interaction is a more direct way of selecting an action, e.g instead
of choosing an erase command, the user could select an eraser tool and
directly erase the desired areas.
Pros: Tools are intuitive and allow real-world metaphors.
Cons: Increases the number of modes of an application.
The proposed interaction techniques employ 2D graphical user interfaces
combined with tool interaction.
4.5.4 Conclusion: 2D Interaction In 3D Environments
It would be a grave mistake to think that just because an application has a
3D scene and allows the user to interact with 3D objects, its interface and the
interaction with it should be exclusively 3D too. In fact, with a few modica-
tions, 2D interfaces and 2D interaction can be more advantageous than their 3D
counterparts in some cases. For instance, 2D interaction on a physical surface
like a workbench or a tablet is precise, ergonomic and provides a sense of feed-
back that you do not nd in 3D interaction. Taking advantage of the benets
of both 2D and 3D interaction techniques by combining them in a seamless way
is a viable strategy in 3D interface design.
37
39. 5 Proposed Interaction Techniques
This section details the proposed setup, including the input and output devices
that were used, and the rst user study of this thesis, which was conducted to
determine the individual strengths and weaknesses of the input devices, and its
results. Then, the two applications, that were developed to demonstrate the
proposed interaction techniques, are introduced, before nally presenting the
interaction techniques themselves.
5.1 Setup
As stated before, the goal is to build an immersive viewer of seismic data.
The keyword immersive stands for the greatest challenge in this endeavour, as
the idea behind the application is to make the user feel like they are actually
interacting with the seismic data and not with just a 2D projection of it. Rather
than working with an abstract view of the data that lacks depth, the user is
supposed to be immersed in the data. The proposed approach tries to realize this
using stereoscopic 3D and intuitive interaction that is optimized for stereoscopy
and, most importantly, does not break the immersion. That means, no clicking
through a barrage of 2D menus and dialogs, no memorizing a dozen of keyboard
shortcuts, and certainly no reading long instruction manuals to learn how to
use the application.
An additional requirement was the design of the application for two use
cases, one being the desktop use case and the other being the stand use case.
The next segments briey outline them.
5.1.1 Desktop Use Case
In the desktop use case, the application is supposed to be used much like how
you would use an application on a personal desktop computer. As you can see in
the draft in Figure 20, the user sits at a desk in front of a monitor, a stereoscopic
3D one in this case, and works with the application using the interaction devices
in front of them. From an ergonomic point of view, this use case is more suited
for actually working with the data for an extended period of time.
Figure 21 shows how the desktop use case looked like during the implemen-
tation of the application. This also happens to be the workspace at which the
proposed interaction techniques were developed.
5.1.2 Stand Use Case
The stand use case requires a much bigger stereoscopic monitor, as the user will
be standing behind a stand further away from the display. Thanks to the bigger
monitor, this is the more immersive mode, optimal for immersing oneself with
the data and analyzing it.
38
40. Figure 20: An early draft of the Desktop Use Case.
Figure 21: The Desktop Use Case during development.
39
41. Figure 22: An early draft of the Stand Use Case.
Figure 23: The Stand Use Case during implementation.
40
42. 5.1.3 Proposed Input Devices
The following input devices were considered in the implementation.
1. Dell Keyboard
Figure 24: A Dell Keyboard [@DUK].
The keyboard is a very versatile input device and can be adapted to be
used for pretty much every task with its many keys. It is mainly used for
quickly accessing system control functionalities with hotkeys, but many
games, e.g. rst-person shooters, still use them for the navigation inside
a 3D scene.
2. Dell Mouse
Figure 25: A Dell Mouse [@DUM].
The mouse with its precise 2D input and two buttons, three if you count
the wheel as a button, has been an indispensable input device for many
decades now. Together with the keyboard, it is used in every seismic
interpretation system and it does not look like it is going to change anytime
soon. These two devices were included as traditional input devices for the
user to fall back to if the other newer devices fail to full their tasks.
41
43. 3. 3Dconnexion SpaceNavigator for Notebooks
Figure 26: A SpaceNavigator [@BB].
The SpaceNavigator represents 3D mice in this implementation. With its
six Degrees of Freedom, the SpaceNavigator is commonly used in the non-
dominant hand for navigation tasks, since every possible 3D motion can
be simulated by pushing, pulling, twisting or tilting it.
4. Leap Motion
Figure 27: A Leap Motion [@TC].
The Leap Motion Controller is a motion sensing input device manufac-
tured by Leap Motion, Inc., that can recognize hands, ngers and nger-
like objects, and track their discrete positions, gestures and motion (See
Figure 28). The small USB device was designed to be placed facing upward
on a desk between the user and the computer screen. Using a combination
of three built-in infrared LEDs and two monochromatic infrared cameras,
the device observes a cubic area above it with a eld of view of about 150
degrees at an eective range of 25 to 600 millimeters (See Figure 29).
The LEDs emit their IR light in a specic 3D pattern of dots, while the
cameras capture depth information at a rate of over 200 frames per sec-
ond. As the device itself only oers minimal onboard processing, the frame
42
44. Figure 28: Hands getting tracked by the Leap Motion [@NW].
data has to be sent via USB to the host computer, where the Leap Mo-
tion drivers compute 3D position information of the tracked objects by
comparing the 2D frames generated by the two cameras with the help
of a yet to be disclosed complex algorithm [Gun+14]. According to the
manufacturer, the Leap Motion tracks all 10 ngers of the user up to
1/100th of a millimeter [@LEAP]. The Leap Motion was included in this
implementation, because it is a considerably cheap and powerful 3D input
device.
Figure 29: Leap Motion Hardware [@DB1].
43
45. 5. Wacom Cintiq Companion Pen/Touch LCD tablet
Figure 30: Wacom Cintiq Companion [@DB2].
The Wacom Cintiq Companion is not just another input device. It is a
computer with a powerful Intel Core i-7 processor and a 13.3 inch Full HD
built-in display. It provides two dierent kinds of 2D input, pen and multi-
touch [@WACOM]. While the multi-touch is not any dierent than the
multi-touch on a regular Windows 7/8 tablet, the pressure-sensitive pen
input represents the current standard for pen tablets, and is well worth
taking a closer look.
Figure 31: Wacom's originally developed EMR Technology [@WC1].
Wacom tablets use slim, lightweight electronic pens that have no need of
an obstructive cord or built-in power supply, along with a non-contact type
sensor board incorporated into the tablet surface. Both the pen and the
44
46. board make use of Wacom's originally developed Electro-Magnetic Res-
onance (EMR) Technology. A magnetic eld is generated by the sensor
board surface and induces a weak energy in the pen's resonant circuit,
which in return sends a magnetic signal back to the sensor board surface
(See Figure 31). This allows the board to detect the pen's coordinate po-
sition and angle, as well as its speed and writing pressure, among others.
Due to the magnetic eld, the sensor board can detect the pen's coor-
dinates from a small distance, even before the pen touches the tablet's
surface. This is called hovering (See Figure 32). Once the pen makes
contact with the surface, a writing pressure of 256 to 1024 steps can be
detected, which is widely used in the eld of drawing applications [@WC].
Figure 32: Wacom pens can be detected by the built-in sensor from a small
distance [@WC2].
5.2 Target Cubes - An Input Devices Test
With a wide range of 2D and 3D input devices to choose from, a reliable method
to determine which devices are suitable for which interaction task proves neces-
sary. In other words, an interaction study is necessary. By performing a simple
interaction task using dierent devices under the same conditions, you can eec-
tively compare the devices under certain aspects, such as ease of use, speed and
accuracy. There have been countless interaction studies in the past, but in most
cases, they were very general studies, which, for example, examine whether one
kind of input devices is better than another or not, or the tested devices are
either outdated or hard to come by. Therefore, a new interaction study had to
be specially developed for the set of input devices that were considered for the
SeisViz3D project. For that purpose, I have come up with the Target Cubes
test, a simple yet eective way of comparing input devices in terms of accuracy,
intuitiveness and usability.
45
47. Figure 33: Screenshot of the Target Cubes test.
5.2.1 Participants
The test was carried out in the week of April 28th to May 2nd, 2014. In total,
20 people have participated in the study, of which 11 were computer scientists
and 9 were geologists. The participants were of varying ages, from 24 to 63.
The mean age was 40.1 and the median was 33.
5.2.2 Apparatus
The system the test ran on was a Dell T3400 with an Intel Core 2 Duo E8500
processor and an Nvidia Quadro 2000 graphics card. The test software was
written in C++ with OpenSceneGraph, while the interface on the tablet was
written in C# with Microsoft XNA. The test was carried out completely in
stereoscopic 3D, using an Nvidia 3D Vision Pro Kit. OpenSceneGraph supports
a number of dierent stereo modes, anaglyphic stereo with red/green or red/cyan
glasses, quad-buered stereo, either as active stereo with shutter glasses or as
passive stereo with polarized projectors and glasses, and horizontal/vertical split
window stereo. In this implementation, active quad-buered stereo was used
with Nvidia shutter glasses.
46
48. 5.2.3 Procedure
In this study, the user has to control a yellow cursor cube in a 3D grid of cubes
using an input device, move it to a green target cube and select it. There
are depth cues to help the tester orientate themselves in 3D in form of cubes
connecting the cursor cube to all six sides of the 3D grid. The test was carried
out with ve dierent input devices under two dierent neness levels (7 and
19). The neness of the grid determines how many cubes the 3D grid is divided
into in each dimension.
Selecting the target cube in the ner grid, with neness 19, stands for tasks
that require precision such as selecting a point in 3D, while not so precise tasks
like selecting 3D objects inside a 3D scene is represented by the rougher grid,
with neness 7.
Figure 34: Comparison of the two dierent levels of neness. Left: Fineness =
9; Right: Fineness = 19.
5.2.4 Tested Input Devices
Here is an overview of the interaction devices and their controls:
1. Dell Keyboard (KBRD)
ˆ The arrow keys translate the cursor in the XZ-plane and the W, S
keys along the Y-axis. Pressing the Enter key selects a cube.
47
49. 2. Dell Mouse (MOUSE)
ˆ Moving the mouse translates the cursor in the XY-plane and the
scroll wheel along the Z-axis. To select a cube, you can either click
or press the Enter key on the keyboard.
3. 3Dconnexion SpaceNavigator for Notebooks (SPCNVGTR)
ˆ Pushing and pulling the SpaceNavigator left and right moves the
cursor along the X-axis, up and down along the Y-axis and forward
and back along the X-axis. The Enter key selects a cube.
4. Leap Motion (LPMTN))
ˆ Moving one of your hands while pointing with the index nger moves
the cursor in the 3D grid. To select a cube, you can either use the
so-called KeyTapGesture, that is recognized when you tap with the
tip of the index nger, or press the Enter key.
5. Wacom Cintiq Companion Pen/Touch LCD tablet (TABLET)
Figure 35: Screenshot of the Target Cubes test tablet user interface.
48
50. ˆ Using the pen or your ngers, you can pick two 2D points in a top
and front view of the 3D grid, respectively, which are combined into
a 3D point in the 3D grid. You can select a cube by either pressing
a button on the tablet user interface or the Enter key.
5.2.5 Measured Times And Survey Results
00:00
00:07
00:14
00:21
00:28
00:36
00:43
00:50
Fastest time (Fineness = 7) Fastest time (Fineness = 19) Average time (Fineness = 7) Average time (Fineness = 19) Median time (Fineness = 7) Median time (Fineness = 19)
Interaction times
Keyboard Mouse SPCNVGTR LPMTN TABLET
Figure 36: Measured Interaction Times.
We will primarily take a look at the median times, as they are the most resistant
to outliers.
ˆ In the grid of neness 9, the fastest median times were achieved with the
tablet, Leap Motion and the mouse respectively, while the keyboard and
the SpaceNavigator were the slowest.
ˆ In the rougher grid with a neness of 19, the median times were quite
similar, with the tablet being the fastest and the mouse being a close
second, while the Leap Motion was a tad slower. This time, the keyboard
did a bit better than the slowest device, the SpaceNavigator.
In addition to measuring the times, each tester had to ll out a questionnaire
with six questions in total. The purpose of the questionnaire was to nd out
how the testers felt about each input device, its usability and ergonomity. Albeit
not the main focus of this study, there were two questions about the testers'
impression of the stereoscopic 3D too. Let us now go over each question of the
questionnaire and analyze their answers.
49
51. 1. How well were you able to work with the interaction devices?
Q1: KEYBOARD Q1: MOUSE Q1: SPCNVGTR Q1: LPMTN Q1: TABLET
Q1: How well were you able to work with the interaction devices?
Very
Well
Normal
Badly
Very
Figure 37: The results of Question 1.
ˆ As expected, pretty much all participants were able to work well with
the keyboard and the mouse, as they were the most experienced with
using them.
ˆ However, it is remarkable, that the tablet received the most positive
votes even though most of the participants used a tablet for the rst
time.
ˆ They found it more dicult to operate the Leap Motion and the
SpaceNavigator, as it was a completely new device for almost all
participants.
ˆ But the much better rating of the Leap Motion shows that most
of the participants were able to get accustomed with it, while the
SpaceNavigator received mostly negative votes.
50
52. 2. How ergonomic did you nd the interaction devices?
Q2: KEYBOARD Q2: MOUSE Q2: SPCNVGTR Q2: LPMTN Q2: TABLET
Q2: How ergonomic did you find the interaction devices?
Very
ergonomic
Ergonomic
Normal
Tiring
Very
tiring
Figure 38: The results of Question 2.
ˆ This question produced a distribution of votes that is very similar
to question 1, with the tablet receiving the highest rating and the
mouse and keyboard as close seconds.
ˆ The participants were obviously comfortable working with the two
devices they were the most familiar with, but it also seems like tap-
ping with your nger and clicking with a pen on the tablet was even
easier than clicking with a mouse and pressing keys on a keyboard.
ˆ The SpaceNavigator and the Leap Motion received mostly negative
votes. Apparently, the sensitivity of the SpaceNavigator and the
exhausting gesture of keeping your hand in mid-air and pointing with
your index nger for the Leap Motion made it rather tiring to work
with them.
51
53. 3. How comfortable was working in stereoscopic 3D?
Q3: Testers
Q3: How comfortable was working in stereoscopic 3D?
Very
comfortable
Comfortable
Normal
Uncomfortable
Very
uncomfortable
Figure 39: The results of Question 3.
ˆ The stereoscopic 3D, albeit not the focus of this study, was generally
well-received.
ˆ Four participants loved it, eleven were comfortable with it and the
rest were not bothered by it.
4. Did working in stereoscopic 3D make the task easier or more
dicult?
Q4: Testers
A lot
easier
Easier
Same
Harder
A lot
harder
Q4: Did working in stereoscopic 3D make the task easier or more difficult?
Figure 40: The results of Question 4.
ˆ The vast majority of the participants found that the stereoscopic 3D
helped them perform the task and only two felt that it was more
52
54. harmful than helpful.
ˆ Regarding this question, it would have been more interesting to have
the participants perform the test without the stereoscopic 3D too,
but I chose not to for the following two reasons:
As already mentioned before, working in stereoscopic 3D was not
the focus of this study. The focus lies on the interaction devices.
Carrying out the test once in stereoscopic 3D took about 15
minutes including the two dierent neness levels and the time
needed to ll out the questionnaire. Doing the whole thing again
without stereoscopic 3D would have made the test way too long
and tedious.
Another problem is that extending the test and making the par-
ticipants perform the same test twice would cause them to get
accustomed to it and achieve better times the second time.
5. Which interaction device would you use for very precise tasks?
0
2
4
6
8
10
12
14
16
Votes
Interaction devices
Q5: Which interaction device would you use for very
precise tasks?
Q5: KEYBOARD
Q5: MOUSE
Q5: SPCNVGTR
Q5: LPMTN
Q5: TABLET
Figure 41: The results of Question 5.
ˆ This question and the one after it may be the most important ones in
the questionnaire. After all, the whole point of this study is to deter-
mine which of the interaction devices are suited for which interaction
tasks.
ˆ As for the answers, most participants would use the tablet and the
mouse for very precise tasks. Some would opt for the keyboard, while
only a few voted for the SpaceNavigator and the Leap Motion.
53
55. 6. Which interaction device would you use for rougher tasks?
0
2
4
6
8
10
12
14
16
Votes
Interaction devices
Q6: Which interaction device would you use for
rougher tasks?
Q6: KEYBOARD
Q6: MOUSE
Q6: SPCNVGTR
Q6: LPMTN
Q6: TABLET
Figure 42: The results of Question 6.
ˆ For not so precise tasks, the tablet with its pen and touch input got
the most votes by far. The other interaction devices are pretty close
together, with the SpaceNavigator getting the second most votes and
the tablet getting the fewest.
To summarize, the participants liked working with the lower-dimensional
devices, the mouse and the keyboard, since they were already familiar with
them. It needs to be noted, however, that the interaction with the keyboard
was found to be slower and more tedious due to its 1D input allowing only
movement in one dimension at a time. Despite their lack of experience with
the newer devices, the participants quickly grew accustomed to the interaction
with the tablet and the Leap Motion. The SpaceNavigator with its steeper
learning curve received generally negative votes from all participants, which
was, according to the comments in the questionnaire, mainly due to its high
sensitivity making it dicult to move the cursor cube in one direction at a time,
causing it to jitter around the target cube. In addition, some of its gestures,
e.g. pulling the SpaceNavigator up away from the desk and pushing it down to
move the cursor cube along the vertical axis, were found to be unnatural and
dicult to pull o.
In conclusion, it was decided to exclude the SpaceNavigator and the key-
board as primary pointing devices for interaction techniques. The keyboard
will still be used to interact with the GUI of the application, providing hotkeys
and text input, while the SpaceNavigator has not lost its value as a navigation
device in the non-dominant hand of the user. For tasks requiring precision, such
as selecting a point in 3D, drawing on 2D slices, the tablet will be used. For not
54
56. so precise tasks, on the other hand, the Leap Motion will be used predominantly.
The mouse, as an all-rounder, will serve as an alternative interaction device to
fall back to, when a user fails to get accustomed to working with the tablet or
the Leap Motion.
5.3 User Interface
This implementation consists of two applications, the Main Program and the
Tablet Program. The Main Program contains the volume renderer and processes
the input from the input devices including the tablet, while the Tablet Program
provides an alternative user interface. The two programs have be in sync at
all times, which is accomplished with messages sent over a network connection.
The following subsections introduce the user interfaces of the two applications.
5.3.1 Main Program
Figure 43: Screenshot of the Main Program user interface.
55
57. The Main Program has a simple design (See Figure 43). With a main menu bar
and a mode bar featuring four dierent modes, the user can quickly access the
functionality they need.
Main Menu Bar
ˆ File - For loading a volume data set and exiting the program.
Load. . . - Opens a le dialog that lets the user choose the data to
load.
Exit - Shuts the application down.
ˆ Edit - Lets the user add slices and change the volume probe size.
New Slice. . . - Opens the NewSliceDialog to add a new slice to the
scene (See Figure 44).
Figure 44: Screenshot of the New Slice Dialog.
Change Volume Probe Size. . . - Lets the user change the size of
the volume probe.
ˆ Options - Options to toggle the visibility of scene objects.
Toggle Data - Turns volume data visible/invisible.
Toggle Active Fault - Turns the selected fault visible/invisible.
Toggle All Other Faults - Turns all faults but the selected fault
visible/invisible.
Toggle Stereo - Turns stereoscopic visualization on/o.
ˆ View - Oers predened views of the scene.
Front - Switches to the front view of the scene.
Back - Switches to the back view of the scene.
Right - Switches to the right view of the scene.
56
58. Left - Switches to the left view of the scene.
Top - Switches to the top view of the scene.
Bottom - Switches to the bottom view of the scene.
Mode Bar The program has the following four modes:
1. Navigation mode
ˆ This is the default mode, which, as the name suggests, allows the
user to freely navigate through the scene, scale and rotate it to their
needs, using the input device of their choice.
2. Annotation mode
ˆ This mode is for adding ag annotations into the scene. The user
can freely move the cursor around and add an annotation using the
input device and the interaction technique of their choice.
3. Interpretation mode
ˆ In this mode, the user can add or remove all three types of slices, in-
line, crossline and timeline slices. The slices can then be individually
shifted through the seismic data.
4. Fault Creation mode
ˆ This mode is the heart of a typical fault interpretation workow, as it
lets the user precisely add fault points into the scene with the input
device and interaction technique of their choice, which are automat-
ically triangulated into fault surfaces.
5.3.2 Tablet Program
The Tablet Program (See Figure 45) serves as a secondary screen and user
interface for the Main Program, which means that they have to be in sync at
all times. This is done by sending XML messages back and forth between the
two programs. The messages can contain the current mode the program is in
and the transformation matrix of the scene etc. Naturally, the Tablet Program
oers all four modes that the Main Program oers plus a number of additional
sub-modes for each of the four modes.
In all four modes, the user can navigate through the scene by rotating it
with one nger and scaling it with two ngers, using the pinch-zoom gesture.
The pen input is used to select points and slices, depending on the mode the
application is in. All buttons can be clicked with both the nger and the pen.
1. The Navigation mode is essentially the same as the Navigation mode in
the Main Program. It shows the bounding box of the volume data with
its slices.
57
59. Figure 45: Screenshot of the Tablet Program user interface.
2. The Annotation mode oers three dierent sub-modes, which stand for
one point selection method each. Once a point is selected, the user can
choose to add an annotation, or go through already added annotations to
delete them.
ˆ Overview1: This sub-mode lets the user select a point with the pen,
using the 3D point selection method.
ˆ Overview2: This sub-mode lets the user select a point with the pen,
using the TOP|FRONT point selection method.
ˆ Buzzer: This sub-mode is automatically activated when the user
tries to select a point using the Leap Motion and provides a big
button, since the Leap Motion itself has no buttons.
3. The Interpretation mode works the same way as the Interpretation mode
of the Main Program. The user can add slices, select already added ones
to shift them through the data or delete them.
4. The Fault Creation mode works just like the Annotation mode, it even
has the same three sub-modes. The only dierence is that you can add
58
60. fault points instead of annotations. The last added point can be undone,
and already added fault surfaces can be selected and deleted.
5.4 Seismic Interpretation Workow
The program's functionalities are presented as typical workows for the tasks
Navigation, Point Selection, Annotation, Slice Handling, and Fault Modelling.
5.4.1 Navigation
1. Switch to the Navigation mode.
2. Use one of the following navigation methods to rotate or scale the scene:
ˆ With the Mouse:
Navigating the scene using the mouse works in a rather conventional
way that is found in most other 3D programs.
Rotating:
You can rotate the scene by dragging the mouse while keeping
the left mouse button pressed. The translation of the mouse
coordinates is projected onto a sphere, a trackball, resulting in a
rotation along the surface of the trackball (See Figure 46). This
way, the user can generate rotations about all three coordinate
axes with a 2D device like a mouse. To rotate around the Y-axis,
click in the center of the scene and drag straight left or right. To
rotate around the X-axis, click in the center of the scene and drag
straight up or down. Finally, to rotate around the Z-axis, click
in the area outside the trackball and drag around the trackball.
Figure 46: A 2D translation is projected onto a rotation along the surface of a
sphere.
Scaling:
You can scale the scene up and down evenly by dragging the
mouse up and down while pressing the right mouse button.
ˆ With the Tablet:
Rotating:
Rotating the scene with the tablet is largely similar to the track-
ball rotation with the mouse, as you can invoke the same rota-
tions by pressing one nger on the tablet and dragging it around.
59
61. Scaling:
To scale the scene, do the pinch-zoom gesture with two ngers.
ˆ With the Leap Motion: (See Figure 47)
Rotating:
To rotate the scene, you need both hands. You can only rotate
about one axis at a time, as being able to rotate about all three
axis at the same time makes it very dicult for the user to make
precise, controlled rotations. This can be illustrated by the fact
that it is close to impossible to undo an unwanted rotation about
a random axis in 3D, but if it is around one of the three main
axis, you can easily rotate back to undo the rotation. To rotate
around the x-axis, turn your right hand into a st and open your
left hand. Then move your left hand forward and back while
keeping your right hand still. To rotate around the y-axis, do
the opposite. Turn your left hand into a st and open your
right hand. Then move your right hand forward and back while
keeping your left hand still. Finally, to rotate around the z-axis,
open both hands and move them in opposite vertical directions
to rotate into the direction of the lower hand.
Scaling:
You can scale the scene with the Leap Motion by moving one
hand forward or back and keeping it still. The further the center
of your palm is away from the point right above the Leap Motion,
the faster the scene gets continuatively scaled. However, there is
a no-scale zone right above the Leap Motion, where no scaling
occurs. This is to prevent unwanted scaling. To stop scaling,
you can either turn your hand into a st or move your hand to
the no-scale zone.
Figure 47: The navigation gestures with the Leap Motion: (1) Default gesture;
(2) Gesture to scale the scene; (3) Gesture to rotate around the x-axis; (4)
Gesture to rotate around the y-axis; (5) Gesture to rotate around the z-axis.
5.4.2 Point Selection
To select a point, you have to move the scene cursor to the desired position in
the scene. We propose four dierent ways of controlling the cursor in 3D.
ˆ With the Mouse:
The 2D coordinates of the mouse are mapped to a XY cursor plane in
60
62. the scene that lies perpendicular to the view direction, so that you can
reach every point in this plane by moving the mouse around. Use the
mouse wheel to change the Z-coordinate of the cursor, and with it the Z-
coordinate of the cursor plane. Note that scrolling with the mouse wheel
only creates discrete up and down events, which is why a step size has
to be dened. If the step size is 1, you could scroll through every point
of the scene along the Z-axis, but it would make going from one point to
another a slow and tedious task. We used a step size that depends on the
size of the data in Z-direction.
ˆ With the Tablet:
The tablet oers the following two point selection methods:
3D method:
The 3D method essentially emulates the selection of points with the
mouse. The 2D coordinates of the pen are mapped to the same XY
cursor plane in the scene, so that you can move the cursor around
in said plane by drawing on the tablet with the pen. By sliding one
nger up and down on the scroll eld on the left of the tablet user
interface, usually with the hand that is not holding the pen, you can
scroll through the scene in the same way you can with the mouse
wheel (See Figure 48). However, sliding your nger on a tablet's
surface generates a much bigger number of events, and allows a much
smoother scrolling through the scene along the Z-axis. In this case,
the step size is per default 1, i.e. every point in the scene can be
reached with a reasonable amount of eort and time.
TOP|FRONT method:
The TOP|FRONT method takes an entirely dierent approach, as it
requires the user to choose two 2D points from two dierent view-
points, one from the top of the scene and one from the front, and
combines them into one 3D point. For this purpose, the tablet user
interface is divided horizontally into two halves: the left side repre-
sents the TOP view, while the right side stands for the FRONT view
(See Figure 49). By drawing with the pen on the TOP and FRONT
sides, the user can move the cursor along the XZ and XY planes,
respectively. Since you can set the X-coordinate in both views, it
is recommended to set only the Z-coordinate in the TOP view rst,
before setting the X- and Y-coordinates in the FRONT view, or to
set the y-coordinate in the FRONT view rst, before setting the X-
and Z-coordinates in the TOP view.
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63. Figure 48: The tablet user interface when using the 3D point selection method.
On the left, you can see the sliding eld that emulates the mouse wheel.
Figure 49: The tablet user interface when using the TOP|FRONT point selec-
tion method.
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