FGS 2011: Making A Game With Molehill: Zombie Tycoon

Making a game with Molehill: Zombie Tycoon
Luc BeaulieuCTO – Frima Studio
Jean-Philippe AuclairLead R&D Software Architect

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

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
State of Flash

Pros:
GPU Accelerated API
Relies on DirectX 9, OpenGL 1.3 and OpenGL ES 2.0
Native Software fallback
Cons:
No point sprite support, branching, MRT, depth buffer
No CPU threading support
Native Software fallback
Molehill’s API Presentation

This Page Intentionally Left Green

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

Frima 3D File Format
Many 3D engine for flash try to support multiple input format
…Or try to use generic format such as ColladaXML
Using a format optimized for 3D game made in Flash
Small File Size
Small Memory footprint
No processing required

Frima 3D File Format
Supporting one Pipe-line for optimized result
Using a AIR tool to read Collada files, parse them and fill final game Model/Animation objects
Native object serialization (AMF)
Native ByteArray Compression

Texturing in Molehill
Adobe Texture Format (ATF)
Simple PNGs are expended in video memory
Native support for multi-device publishing
One file containing 3 encoding: DXT1, ETC1 and PVRTC
Does not support transparency
Contain the MipMapping of the texture
1.3x bigger than original PNG
Transparency
Use PNGs with indexed color
Sample a “alpha mask texture” in the pixel shader

Texturing in Molehill
Texture type image
Graph videospace

Zombie Re-Animation
Techniques
Matrix linear blending
DualQuaternion linear blending
Molehill Constraint
Vertex Shader constants limits: 128 Float4

Animation techniques
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 linear blending can cause loss of volume when joints are twisted or extremely bent
Matrix (left) / Dual Quaternion (Right)

Transitions & interpolation
Too Much
Animation transition require two sets of bones
Idle blending to walk
Same thing for frame interpolation (ex: Bullet time Animation)

You have to choose

Optimizing the Particle System

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

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
UsingFastByteArray (alsoknown as Alchemymemory or DomainMemory)
Using Azoth, properties updates were 10 times faster
Batching draw calls using the same texture
Using a 100% GPU particle system
It’sexpensive on the GPU
Support onlylinear transformation
Zero CPU required

Particle System

Lights & shadows
Techniques
ShadowMap & LightMap
Dynamic lighting
Fake Volumetric lights
Fake projected shadows

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

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

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 lights particle are “additive”, if an object is behind the lights, it will look brighter

Lights & shadows

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

CPU Post-Processing
Possibility of reading the BackBuffer
Althought not suggested for performance reason, it is possible to draw something and readback in the same frame to work on the final BitmapData with as3 code.
Effects
Bloom
Blur
Depth of field
Much more!
Normal
With Bloom

Profiling and Debuggingtools (CPU)
FlashDevelop
Most of the production is using FlashDevelop
Now with a profiler and a debugger, it’s very easy to work with it
Flash Builder Profiler
Profile Function calls
Profile Memory allocation
FlashPreloadProfiler
Profile Function calls
Profile Memory allocation
Profile Loaders status
Can be used in Debug/Release & browser/Projector
FlashDevelop
FlashBuilder Profiler

Profiling and Debuggingtools (GPU)
Pix for windows
List of API call
Shaders assembly code
Pixel debugger
Texture viewer
Intel® Graphics Performance Analyzers (GPA)
Render in wireframe
Profile Vertex and Pixel shader performance
Visuallize overdraw and draw call sequence
Save a frame, and make real time experiment
Identification of bottle necks
PIX
GPA

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

VertexBuffer
IndexBuffer
Vertex Constants
MipMapping
Quaternion
Billboard
What?

Character animation:
Matrixlinearblending:
128 Float4 VertexConstant – WorldMatrix – ViewProjmatrix = 120Float4
120Float4 / / 3Float4 per bone = 40 bones in the constants
Bullet time and transitions requiretwo sets of bones: 40/2 = 20 bones per character max
DualQuaternionlinearblending:
128 Float4 VertexConstant – WorldMatrix – ViewProjmatrix = 120Float4
120Float4 / / 2Float4 per bone = 60 bones in the constants
Bullet time and transitions requiretwo 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)
Bonus Slide: The maths!

CheatSheet
Achievement: Geek

Achievement: Super Geek!

Thank You!
Questions?
Contact
Luc Beaulieuluc@frimastudio.com
Jean-Philippe Auclairjpauclair@frimastudio.com
@jpauclair
jpauclair.net

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FGS 2011: Making A Game With Molehill: Zombie Tycoon

by mochimedia on Mar 11, 2011

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FGS 2011: Making A Game With Molehill: Zombie Tycoon — Presentation Transcript