Mike Acton, Insomiac Games. 6.189 IAP 2007 MIT6.189 IAP 2007Lecture 16Introduction to Game DevelopmentIntroduction to Game Development(on the Playstation 3 / Cell )●Mike Acton –Engine Director, Insomniac Games–< macton @ insomniacgames.com >–Director, CellPerformance.com–< macton @ cellperformance.com >Different Types of Game Development●Casual●Console●PC●Handheld●Cellphone●Single Player ●Multi PlayerConsole Development Priorities●The code itself is not that important.●The design of the data affects performance more than the design of the code.●Ease of programming is either a minor or non-priority.●Portability is not a concern.●Performance is still king.Development Team●Artists–Animation, Shader, Texture, Modeling–Environment, Lighting, ...●Designers–Systems, Level, ...●Writers●Producers●Programmers–Gameplay, Engine, AI, Special Effects, –Sound/Music, ...What Impacts Game's Technical Design?●Type of game●Framerate●Schedule●Cost●Hardware●Compilers●...●How does this affect code reusability?●How does this affect cross-platform design?What are the major game modules?●Memory management●Math●Collision●Physics●Static graphics●Animation●Procedural graphics●Lighting●Loading, streaming●Scene graph●AI●Compression●Sound, Music●Special Effects●State machines●Scripting●Motion control●...Overview●How does programming on the Playstation 3 affect the (macro) design of the major systems?●Overview of design process for a specific system (Animation).Structure Design (1)●Conventional structures are (surprisingly?) needed very little in engine-level SPU code.–Data is compressed–Data is sorted by type (i.e. Fewer flags)–Data is organized into blocks or streams–Data is accessed only in quadwordsStructure Design (2)●Organize data carefully:–Prefer fixed (known) size blocks–Fundamental unit: 128 bytes (Cache line)–Fundamental unit: 16 bytes (Quadword)–Prefer uniform data●Minimum working sizes:–4 x 2 x 64 bits–4 x 4 x 32 bits–4 x 8 x 16 bits–4 x 16 x 8 bits–4 x 128 bitsBasic Math●e.g. Vector Class–Usually the first thing a programmer will make, but consider:●SIMD, Altivec vs. SPU instruction set●Floats vs. Double vs. Fixed-point●SPU floating-point format●Component access–... There's no value here.Memory Manager●Static allocation is preferred to dynamic●Most data patterns are known in advance●When designing allocator, consider:–Page sizes–LRU is most common, but pretty bad.–Hierarchy of allocations–Fragmentation is a non-issue for well planned architectures–Remember cache line alignment.–SPU transfer blocks, 16KCollision Detection●Affects high-level design–Deferred results–Grouped results●SPU decomposition for:–Static geometry in scene–Dynamic geometry in sceneProcedural Graphics●Patch size●Filter types●Sync of source reads●Sync with GPU●SPU vs. RSX●Particles●Cloth●Fonts●Textures●Parametric geometry●...Geometry databases●No scene graph●Domain information linked by key●Cache and TLB affect design choices–e.g. Static geometry lookup (Octree, BSP, etc.)●Geometry lookups on SPU–Spatially pre-sort–Multiple simultaneous lookupsGame Logic●State machines–Size affected by SPU–Deferred results–Logic lines can be deferred●Scripting–Interpreter size–Multiple streams to hide memory accesses●Motion control–High-level sync (Animation, AI, Physics)Animation (1)●Starting with the basics:–Simple playback, animation channels●Related data●e.g. Rotation + Translation + Scale = Joint–Euler vs. quaternion●Euler: More compressible●Quaternion: Less messy●Gimbal lock is manageable in practice.–Format, double vs. float vs. half vs. fixed-point–Rotations: Degrees, radians or normalized?Animation (2)●Animation frame storage–Basic 9 channels (raw)–Uniform channels●Plus uniform channel map●Plus uniform channel count–X Number of joints–Decide on max channelsAnimation (3)●Channel curve fitting–Closer to root, tighter fit.–e.g. Simple spline●Store time values●Problem: Looping scalars●Problem: Unlimited lengthAnimation (4)●e.g. Spline segments–Plus storage for time maps–Plus segment lookup time–Advantage: Can re-order blocks–Advantage: Long lengths OK–Disadvantage: Less compressable–Advantage: Solves scalar loop problem●Summarize: DMA and transform.Animation (5)●e.g. Adding dynamic channel support–Add uniform data table●Maximum dynamic channels with linkage, or...●All uncompressed–Add (simple) contraints●Max change●Max range●Max acceleration (impacts storage)–Blend information–Summarize: DMA and transform.Animation (6)●More on mixing:–Phase matching–Transitions–Translation matching●Drawing animated geometry–Single or double buffer joints:●Single: Requires more organization●Double: More memory, more flexible.Optimization●Required for practice●Impacts design●NOT the root of all