This is a course on the theoretical underpinnings of 3D Graphics in computing, suitable for students with a suitable grounding in technical computing.

1. CREATING A 3D IMAGE
Michael Heron

2. INTRODUCTION
 In this lecture we are going to look at the process
we go through in order to build a 3D image.
 At least in theory.
 Will need to wait until the lab before we do it For Reals.
 Two main techniques for doing this.
 Line Mode
 Box Mode

3. TERMINOLOGY
 Face
 A simple shape used to make up a more complex
shape.
 Also known as a polygon
 Vertex
 A corner point of a polygon
 Edge
 A line represented by two connected vertexes

4. CREATING A 3D OBJECT
 We need to do several things.
 Define the geometry of the shape.
 Apply transforms to set
 Location
 Scale
 Rotation
 Define surface details.
 Textures
 We do this for each object in a scene.
 We’ll talk about only one.

5. DEFINE THE GEOMETRY
 How do we define the geometry?
 We choose between two main ways.
 Or a hybrid of the two.
 First way is to draw each point in the shape.
 For large, complex shapes – extremely difficult.
 The more polygons we have, the more difficult this
becomes.
 This is the line mode of drawing shapes.
 There be dragons.

6. DEFINE THE GEOMETRY
 How do you sculpt an elephant?
 You take a block of marble, and chip away all the bits
that don’t look like an elephant.
 This is the Box Mode of drawing shapes.
 Start with an approximate shape.
 Usually one of the standard geometric principles.
 Manipulate it until it fits your needs.
 Or at least, closely approximates your needs.
 Recommended approach.

7. DEFINE THE GEOMETRY
 A third way is to make use of a representation of a
real object.
 Requires the use of specialised hard-ware
 Which you don’t have.
 The method you choose depends on
 The nature of the object
 Requirements of the model.
 A hybrid approach is usually the best
 Start with a rough shape, draw extensions to handle fine
detail work.

8. 3D REPRESENTATIONAL FORMS
 Several ways to represent 3D Geometry:
 Polygonal.
 Objects approximated by nets of polygons
 A polymesh
 Bicubic
 Objects represented by nets of curved patches.
 Constructive Solid Geometry
 Constructed from sets of basic geometric shapes
 Space subdivision
 Ray-tracing
 We focus primarily on polygonal today.
 Talk about the rest in the next lecture, or thereabouts.

9. SIMPLE POLYMESH
(x1,y1,z1) (x2,y2,z2)
(x3,y3,z3)
(x4,y4,z4)
(x5,y5,z5) (x6,y6,z6)
(x7,y7,z7)(x8,y8,z8)

10. SIMPLE POLYMESH – LOCAL CO-ORDINATES
(0,0,0) (50,0,0)
(50,0,50)(0,0,50)
(0,50,0) (50,50,0)
(50,50,50)

11. SIMPLE POLYMESH - REPRESENTATION
object surfaces polygons vertices

12. SIMPLE POLYMESH - REPRESENTATION
 Represented by a face-vertex mesh
 A list of faces represented by vertexes
 A list of the vertexes and what faces they are part of
 Co-ordinate space of each vertex.
 This provides a mathematical, context independent
representation of an object in its own local space.

13. FACE-VERTEX MESH

14. POLYMESH NOTES
 Shape is only an approximation for complex images.
 Can’t represent a circle.
 Can represent something that is almost a circle
 Level of approximation dictated by polygon count.
 Shading and other detailing approaches can help to hide
shape approximations.
 Ubiquitous representation.
 Graphics cards usually include specialised hardware for
rendering large numbers of polygons.

15. DRAWING AN OBJECT
 Begin with simple starting shape.
 Want to draw a head? Start with a sphere.
 Can add a sphere as a base shape in Blender
 Consider necessary transforms.
 Can do vertex, edge, and face manipulation on
polymesh shapes.
 Can apply basic transforms to part of a shape.
 Can also extrude.
 Used to extend a part of a shape.

16. DRAWING AN OBJECT
 Can also spin basic shapes:
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Modelling_a_Mu
g_using_Spinning_and_Extrusion

17. DRAWING A SHAPE
 Blender provides many different modifiers to
change the basic structure of how you interact with
a shape.
 Mirror allows you to mirror modifications across a
shape.
 Subsurf makes a rough image much smoother and
more organic.
 Lots of these modifiers
 Experimentation is the key

18. MODIFIER - SUBSURF

19. MOLDING A SHAPE
 Back to the elephant.
 How do we turn a simple shape into what we actually want?
 Begin with a sphere
 Elephant body
 Select appropriate faces on that sphere.
 Extrude into legs
 Add another sphere
 The head
 Extrude a trunk
 Extrude a tail
 The rough work is handled using these kind of processes.

20. EXTRUSION
 Extrusion is one of the most powerful tools you
have available in blender.
 Pick a face, and extend it outwards or inwards.
 Used to raise and lower surfaces.
 Can be used to create entirely new surfaces.
 Used to create shapes where shapes did not
previously exist.
 For example, in the coffee cup.

21. EXTRUSION

22. TEXTURING
 Once you have a basic shape you want to make
use of, you can apply various textures to it.
 This changes the colour, and how it interacts with light
sources.
 A base blender scene has three elements.
 A light source (by default, the sun)
 A camera
 A shape

23. TEXTURING
 The texturing system in Blender is extremely rich.
 You can set how your object interacts with light
 You can set the specific kind of rendering to be done
 You can choose transparency and type of textures.
 Most of these will not be visible except in preview
until a scene is rendered.

24. TEXTURES
 Importantly, we can also make use of predefined
bitmaps for a texture.
 We can make use of our own images which get layered onto
the shapes we provide.
 We’ll see more of this later lectures and labs.
 It’s not a simple concept and easier to understand when
shown rather than simply described.
 Experimentation very important.
 Can’t even begin to cover what Blender makes available!

25. SUMMARY
 Polymeshes are the graphical representation must
used.
 We’ll talk about the rest later.
 3D Object created by:
 Representing geometry
 Applying transforms
 Applying textures
 Rendering