2. Making a game with Molehill:
Zombie Tycoon
Luc Beaulieu
CTO – Frima Studio
Jean-Philippe Auclair
Lead R&D Software Architect

3. Session Overview
• State of Flash
• Molehill’s API presentation
• Digging deeper into Molehill

4. State of Flash
• Is Flash Dead?
• FB: Top 10 = 250M MAU
• Desktops: Flash 10 installed on 99%+
• SmartPhones: Flash/Air 200+M, 100 devices
• Streaming: 120 petabytes per month
• Advances in Flash for 3D games
• AS3
• 10.1, 10.2 …
• Molehill

5. Molehill’s API Presentation
• Pros:
– GPU Accelerated API
– Relies on DirectX 9 and OpenGL ES 2.0
– Native Software fallback
• Cons:
– No point sprite support, branching, MRT, depth buffer
– No CPU threading support
– Native Software fallback

7. This Page Intentionally Left Green

8. Digging deeper into Molehill
• Assuming a basic knowledge of 3D development terminology
• Display Layers
• Model/Animation File Format
• Character Animation: Matrix vs Quaternion
• Texturing
• Optimizing the Particle System
• Fast Lights & Shadows
• CPU Post-Processing effects
• Profiling & Debugging tools
• Bonus!
– 3D GameDev Lexicon
– The math explaining all the numbers I’m going to talk about
– Cheat sheets

9. Display Layers

10. Frima 3D File Format
• Many 3D engines for flash try to support multiple input format
• …Or support only generic format such as ColladaXML
• Using a format optimized for 3D game made in Flash
– Small File Size
– Small Memory footprint
– No processing required
Model & Animation File Processing on low-end computer
6000
5250
5000
4000
3000
2000 Time to process (ms)
1000
15
0
Collada XML Frima Binary Format

11. Frima 3D File Format
• Export pipeline
3DS Max Scene
Build Tool
Max Script Exporter
Collada XML

12. Frima 3D File Format
• Export pipeline
Build Tool
Game Serialize (AMF) Game
Model / Animation
Object Compress File

13. Frima 3D File Format
• In-Game usage
Game Uncompress Game
Add To Scene
File Unserialize Object

14. Zombie Re-Animation
• Techniques
– Matrix linear blending
– DualQuaternion linear blending
• Molehill Constraint
– Vertex Shader constants limits: 128 Float4
Zombie:
24 bones

15. Animation techniques
• Matrix linear blending can cause loss of volume when joints are twisted or
extremely bent
• When using matrix, each bone take 3 constants
– Maximum number of bones is 40
• When using DualQuats, each bone take only 2 constants
– Maximum number of bones is 60
Matrix (left) / Dual Quaternion (Right)

17. Transitions & interpolation
• Animation transition require two sets of bones
• Idle blending to walk
• Same thing for frame interpolation (ex: Bullet time Animation)
DualQuaternion 48
matrix 72
0 32 64 96 128
VertexShader constant required for animating a character (24 bones)
DualQuaternion Anim1 (48) Anim2 (48)
matrix Anim1 (72) Anim2 (72) Too Much
0 32 64 96 128
Constant for anim 1 Constant for anim 2

18. File size? Performance?
Animation file size (k)
DualQuaternion 60
matrix 50
DualQuaternion 136
matrix 54
0 32 64 96 128 160 192 224 256
VertexShader assembler instructions for animation processing
Vertex Shader processing time
DualQuaternion 130%
matrix 100%

19. Texturing in Molehill

20. Texturing in Molehill
• The first version of the engine was only using PNGs
• Adobe Texture Format (ATF)
– Texture are kept compressed in Video Memory
– Native support for multi-device publishing
– One file containing 3 encoding: DXT1, ETC1 and PVRTC
– 1.3x bigger than original PNG
– Contain the MipMapping of the texture
– Does not support transparency

21. Texturing in Molehill
• Transparency
– Use PNGs with indexed color
– Sample a “alpha mask texture” in the pixel shader
ATF PNG
Avatar = opaque Fence = Transparent

22. Texturing in Molehill
• Many effects can use ATF when using the good blend modes
• No need for transparency
Splatter = Multiply Fire = Additive

24. Particle System
• Using a divided workload (CPU/GPU) for better performance
– Each particle property update is computed on the CPU at each frame
• Alpha, Color, Direction, Rotation, frame(If SpriteSheet), etc.
– On the GPU
• Applying theses properties
• Expending billboard vertex to face the screen

25. Particle System : Optimization
• How many particle?
– Due to the VertexBuffer and IndexBuffer limits,
– In ZombieTycoon we were limited to around 16383 particles per draw call
• Using Fast ByteArray (also known as Alchemy memory or DomainMemory)
– Using Azoth, properties updates were 10 times faster
• Batching draw calls using the same texture
• Using a 100% GPU particle system
– It’s expensive on the GPU
– Support only linear transformation
– Zero CPU required

26. Particle System

28. Lights & shadows
• Techniques
– ShadowMap & LightMap
– Dynamic lighting
– Fake Volumetric lights
– Fake projected shadows

29. Lights & shadows
• ShadowMap & LightMap
– We used two textures, a “multiplied” ShadowMap and an “additive” LightMap
Diffuse
* ShadowMap
+ Lightmap
= Composite

30. Lights & shadows
• Dynamic lighting
– Lighting required expensive pixel shader, currently limited to 256 instructions
– Zombie Tycoon support up to 7-9 lights (spot or points) per object.

32. Lights & shadows
• Pixel Shader assembly code
– Per light, without Normal/Specular mapping.

33. Lights & shadows
• Fake Volumetric Lights
– Using a few billboard particles, it’s easy to fake a nice and lightweight volumetric lighting
– All object are sampling Shadow and light maps, and since the light particles are “additive”, if
an object is behind the lights, it will look brighter

34. Lights & shadows

36. Lights & shadows
• Fake projected shadows
– We created a particle of a gradient black spot aligned to the ground
– Orientation and scale of the particle depends on light position and intensity

38. CPU Post-Processing
• Possibility of reading the BackBuffer
– Strongly recommended not to use Readback
– Fast pipeline for data from the System memory to Video memory
– VERY slow pipeline from video to system memory
• Effects: Bloom, Blur, Depth of Field, etc.
Motion Blur

39. CPU Post-Processing
Normal Bloom post-processing

40. Profiling and Debugging tools (CPU)
• FlashDevelop (O.S.S.)
– Most of the production is using FlashDevelop
– Now with a profiler and a debugger, it’s very easy to work with it

41. Profiling and Debugging tools (CPU)
• Adobe Flash Builder Profiler
– Profile Function calls
– Profile Memory allocation

42. Profiling and Debugging tools (CPU)
• FlashPreloadProfiler (O.S.S.)
– Profile Function calls
– Profile Memory allocation
– Profile Loaders status
– Can be used in Debug/Release & browser/Projector

43. Profiling and Debugging tools (GPU)
• Pix for windows
– List of API calls
– Shaders assembly code
– Pixel debugger
– Texture viewer

44. Profiling and Debugging tools (GPU)
• Intel® Graphics Performance Analyzers (GPA)
– Render in wireframe
– Profile Vertex and Pixel shader performance
– Visualize overdraw and draw call sequence
– Save a frame, and make real-time experiment
– Identification of bottlenecks

45. Sources & References
• Geometric Skinning with Approximate Dual Quaternion Blending • TD-Matt blog
– http://isg.cs.tcd.ie/kavanl/papers/sdq-tog08.pdf • http://td-matt.blogspot.com/
• Intel® Graphics Performance Analyzers (GPA) • FlashPreloadProfiler
– http://software.intel.com/en-us/articles/intel-gpa/ • http://jpauclair.net/flashpreloadprofiler/
• Pix for windows • Azoth
– http://msdn.microsoft.com/en-us/library/ee417072(v=VS.85).aspx • http://www.buraks.com/azoth/
• Flash in Facebook
• AppData.com
• Flash Stats
Contact •
•
http://adobe.ly/rwXU
http://adobe.ly/gnlUEH
Luc Beaulieu
luc@frimastudio.com
Jean-Philippe Auclair
jpauclair@frimastudio.com
 @jpauclair
 jpauclair.net

46. What it means?
• VertexBuffer
• IndexBuffer
• Vertex Constants
• MipMapping
• Quaternion
• Billboard

47. Bonus Slide: The maths!
• Character animation:
– Matrix linear blending:
• 128 Float4 VertexConstant – WorldMatrix – ViewProj matrix = 120Float4
• 120Float4 / / 3Float4 per bone = 40 bones in the constants
• Bullet time and transitions require two sets of bones: 40/2 = 20 bones per character max
– DualQuaternion linear blending:
• 128 Float4 VertexConstant – WorldMatrix – ViewProj matrix = 120Float4
• 120Float4 / / 2Float4 per bone = 60 bones in the constants
• Bullet time and transitions require two sets of bones: 60/2 = 30 bones per character max
• Max Particle Count
– The VertexBuffer is limited to 65536 vertex, the IndexBuffer is limited to 983040 index of type SHORT
– In theory, you could have up to 327680 triangle in one draw call
– In practice, with no vertex re-use between particles and using quads (4 vertex): 65536/6 = 16383 particle max per
draw call
• Lighting
– With the PixelShader limit of 256 instructions, we were able to fit around 7 to 9 dynamic lights per object (point or
spot light)

48. Achievement: Geek
• Cheat Sheet

49. Achievement: Super Geek!

50. Thank You!
Questions?
Contact
Luc Beaulieu
luc@frimastudio.com
Jean-Philippe Auclair
jpauclair@frimastudio.com
 @jpauclair
 jpauclair.net