Game Programming

1. Game Programming

2. Introduction • Programmers create games • But many great programmers not great game makers • With budget shift, emphasis has shifted • Game content creators are artist and designers • Programmers can be thought of as providing services for content • But fate of entire game rests in their hands

3. Game Platforms

4. Game platform • PC • Single player • Massive multi-player online game ( MMOG ) • Web-based Games • Console ( Video game console ) • Sony PS4 • Microsoft Xbox • Nintedo GameCube • Arcade ( Coin-operated entertainment machine ) • Mobile • Game Boy Advance ( GBA ) • Handheld video game console • iPhone

5. Game development on PC • Designed for office application • Not for entertainment • A virtual memory system • Unlimited memory using • But video memory is limited • PCI/AGP might be a challenge • Open architecture • Compatibility test is important • Development is easy to setup

6. Game development on console • Specific hardware designed for games • Single user / single process OS • In general no hard disk drive (??) • Closed system • Very native coding way • Proprietary SDK • Hardware related features • Limited resources • Memory

7. Sony Playstation Chips • EE: Emotion Engine • GS: Graphics Synthesizer • IOP: Input / Output Processor • SPU: Sound Processing Unit

8. Emotion Engine Components • MIPS R5000 core • VU0 & VU1: Vector Units • GIF: Graphics Interface • DMAC: DMA Controller • IPU: Image Processing Unit • SIF: Serial Interface • INTC: Interrupt Controller • DRAMC: DRAM Controller • TIMER: 4 timers

9. Emotion Engine

10. EE Core • 300 MHz MIPS R5000 CPU • Single floating point multiply/add unit, plus concurrent divider • 128 bit integer ALU • 16K instruction cache, 8K data cache • 16K scratchpad cache • Bus interface • MMU: Memory Management Unit • Core can use VU0 as a vector coprocessor

11. Vector Units • 2 units: VU0 & VU1 (both are on the EE chip) • Each unit has 32 128 bit vector registers • VU0 has 4 floating point multiply/add units capable of producing a total of 8 results per clock cycle • VU0 also has 1 concurrent divide unit capable of producing 1 result every 7 clock cycles • VU1 has 5 MUL/ADDs and 2 dividers • Each VU has a 16 bit integer control processor that runs concurrently and runs control microprograms • VU0 has 4K code & 4K data memory • VU1 has 16K code & 16K data memory • VU0 can also run as a coprocessor to the main core • VIF: Vector Interface. Used for unpacking data (positions, colors, normals) sent into the VU’s. • Single precision floating point, non IEEE754 compliant

12. GS: Graphics Synthesizer • 16 parallel pixel units, 8 if using texture mapping • 4M of on-chip VRAM (video memory) • Performs triangle filling computations • Features: • Texture mapping • Gouraud shading • Z-Buffer • Very simple alpha computations

13. PS2 Processing Summary • CPU core runs main application program. Most AI, physics, game logic, happen on the core. • CPU core can use VU0 as a coprocessor. This allows the CPU to handle more complex physics and geometric computations efficiently. • VU1 runs as an independent processor and acts primarily as a ‘geometry engine’ for computing transformations and lighting for rendering. VU1 has a direct bus to the GS. • GS handles all pixel processing (Z-Buffer, texture mapping, Gouraud shading) and generates the actual video signal • SPU does audio DSP computations and generates the final audio signal • IOP reads input devices and manages DVD drive • DMAC manages and schedules data movement

14. Three Kinds of Code • Gameplay Simulation • Numeric Computation • Shading

15. Gameplay Simulation • Models the state of the game world as interacting objects evolve over time • High-level, object-oriented code • Written in C++ or scripting language • Imperative programming style • Usually garbage-collected

16. Gameplay Simulation – The Numbers • 30-60 updates (frames) per second • ~1000 distinct gameplay classes • Contain imperative state • Contain member functions • Highly dynamic • ~10,000 active gameplay objects • Each time a gameplay object is updated, it typically touches 5-10 other objects

17. Numeric Computation • Algorithms: • Scene graph traversal • Physics simulation • Collision Detection • Path Finding • Sound Propagation • Low-level, high-performance code • Written in C++ with SIMD intrinsics • Essentially functional • Transforms a small input data set to a small output data set, making use of large constant data structures.

18. Shading • Generates pixel and vertex attributes • Written in HLSL/CG shading language • Runs on the GPU • Inherently data-parallel • Control flow is statically known • “Embarassingly Parallel” • Current GPU’s are 16-wide to 48-wide!

19. Three Kinds of Code

20. Game types RPG (Role playing games) AVG (Adventure games) RTS (Real-time strategy games) FPS (First-person shooting games) MMORPG ( Massively multiplayer online role playing game ) Strategy game Simulation game Sports Puzzle games Table games

21. Game team members • Development Team • Producers • Executive producers • Game designers • Programmers • Artists • Level designers • Sound engineers • Sales and marketing • Testers • Game review committee

22. Flowchart of game development Basic Procedures for Game Development Idea Proposal Production Integration Testing Debug Tuning Pre-alpha Concept Approval Prototype Alpha Beta Final > Concept Approval > Prototype > Pre-alpha > Alpha > Beta • Idea • Proposal • Production • Integration • Testing • Debug • Tuning

23. Game Tools

24. Code Development Tools • Compilers (C#, Java, CodeWarrior, GNU) • Debugger • Profiler • Editor • Revision control (CVS, SourceSafe) • Integrated development environment (IDE) • C++, Assembly • Graphics languages: pixel & vertex shaders… • Design analysis tools • Documentation, standards

25. C++ (1 of 3) • Mid-late 1990’s, C was language of choice • Since then, C++ language of choice for games • First commercial release in 1985 (AT&T) • List pros (+) and cons (-) + C Heritage • Learning curve easier • Compilers wicked fast + Performance • Used to be most important, but less so (but still for core parts) • Maps closely to hardware (can “guess” what assembly instructions will be) • Can not use features to avoid cost, if want (ie- virtual function have extra step but don’t have to use) • Memory management controlled by user

26. C++ (2 of 3) + High-level • Classes (objects), polymorphism, templates, exceptions • Especially important as code-bases enlarge • Strongly-typed (helps reduce errors) • ex: declare before use, and const + Libraries • C++ middleware readily available • OpenGL, DirectX, Standard Template Library (containers, like “vectors”, and algorithms, like “sort”)

27. C++ (3 of 3) - Too Low-level • Still force programmer to deal with low-level issues • ex: memory management, pointers - Too complicated • Years of expertise required to master (other languages seek to overcome, like Java and C#) - Lacking features • No built-in way to look at object instances • No built-in way to serialize • Forces programmer to build such functionality (or learn custom or 3rd party library) - Slow iteration • Brittle, hard to try new things • Code change can take a looong time as can compile

28. Java (1 of 3) • Java popular, and recently so for games • Invented in 1990 by Sun Microsystems + Concepts from C++ (objects, classes) • Powerful abstractions + Cleaner language • Memory management built-in • Templates not as messy • Object functions, such as virtualization + Code portability (JVM) (Hey, draw picture) + Libraries with full-functionality built-in

29. Java (2 of 3) - Performance • Interpreted, garbage collection, security • So take 4x to 10x hit + Can overcome with JIT compiler, Java Native Interface (not interpreted) - Platforms • JVM, yeah, but not all games (most PC games not, nor consoles) + Strong for browser-games, mobile

30. Java (3 of 3) • Used in: • Downloadable/Casual games • PopCap games • Mummy Maze, Seven Seas, Diamond Mine • Yahoo online games (WorldWinner) • Poker, Blackjack • PC • Star Wars Galaxies uses Java (and simplified Java for scripting language) • You Don’t Know Jack and Who Wants to be a Millionaire all Java

31. Scripting Languages (1 of 3) • Not compiled, rather specify (script) sequence of actions • Most games rely upon some • Trigger a few events, control cinematic • Others games may use it lots more • Control game logic and behavior (Game Maker has GML) + Ease of development • Low-level things taken care of • Fewer errors by programmer - But script errors tougher, often debuggers worse • Less technical programming required • Still, most scripting done by programmers • Iteration time faster (don’t need to re-compile all code) • Can be customized for game (ex: just AI tasks)

32. Scripting Languages (2 of 3) + Code as an asset • Ex: consider Peon in C++, with behavior in C++, maybe art as an asset. Script would allow for behavior to be an asset also • Can be easily modified, even by end-user in “mod” - Performance • Parsed and executed “on the fly” • Hit could be 10x or more over C++ • Less efficient use of instructions, memory management -Tool support • Not as many debuggers, IDEs • Errors harder to catch - Interface with rest of game • Core in C++, must “export” interface • Can be limiting way interact • (Hey, draw picture)

33. Scripting Languages (3 of 3) • Python • Interpreted, OO, many libraries, many tools • Quite large (bad when memory constrained) • Ex: Blade of Darkness, Earth and Beyond, Eve Online, Civilization 4 (Table 3.2.1 full list) • Lua (pronounced: Loo-ah) • Not OO, but small (memory). Embed in other programs. Doesn’t scale well. • Ex: Grim Fandango, Baldur’s Gate, Far Cry (Table 3.2.2 full list) • Others: • Ruby, Perl, JavaScript • Custom: GML, QuakeC, UnrealScript • Implementing own tough, often performs poorly so careful!

34. Macromedia Flash (1 of 2) • More of a platform and IDE (ala Game Maker) than a language (still, has ActionScript) • “Flash” refers authoring environment, the player, or the application files • Released 1997, popular with Browser bundles by 2000 • Advantages • Wide audience (nearly all platforms have Flash player) • Easy deployment (embed in Web page) • Rapid development (small learning curve, for both artists and programmers) • Disadvantages • 3D games • Performance (interpreted, etc.)

35. Macromedia Flash (2 of 2) • Timeline Based • Frames and Frame rate (like animations) • Programmers indicate when (time) event occurs (can occur across many frames) • Vector Engine • Lines, vertices, circles • Can be scaled to any size, still looks crisp • Scripting • ActionScript similar to JavaScript • Classes (as of Flash v2.0) • Backend connectivity (load other Movies, URLs)

36. Game Development Tools for Artists • 3D tools • Discrete 3dsMax • Maya • Softimage XSI • 2D tools • Photoshop • Illustrator • Motion tools • Motion capture devices • Motion Builder • FiLMBOX

37. Audio Tools • Recording • Composing (ProTools) • Sound effects (Reason) • In-game tools

38. Example Game

39. Gears of War • Resources • ~10 programmers • ~20 artists • ~24 month development cycle • ~$10M budget • Software Dependencies • 1 middleware game engine • ~20 middleware libraries • OS graphics APIs, sound, input, etc

40. Software Dependencies Gears of War Gameplay Code~250,000 lines C++, script code … Unreal Engine 3 Middleware Game Engine ~250,000 lines C++ code DirectX Graphics OpenAL Audio OggVorbis Music Codec Speex SpeechCodec wxWidgets Window Library ZLib Data Compr- ession

41. What are the hard problems? • Performance • When updating 10,000 objects at 60 FPS, everything is performance-sensitive • Modularity • Very important with ~10-20 middleware libraries per game • Reliability • Error-prone language / type system leads to wasted effort finding trivial bugs • Significantly impacts productivity • Concurrency • Hardware supports 6-8 threads

42. 2D game

43. Snake (1970s) Control a snake to move, and avoid hitting to wall or its growing tail.

44. Galaxian (1979 by Namco)

45. Pac Man 1980 by Namco

46. Game & Watch 1980 Game & Watch is a line of handheld electronic games produced by Nintendo from 1980 to 1991. Ball: the first game & watch game

47. Tetris Design by 阿列克謝·帕基特諾夫 （Алексей Леонидович Пажитнов）in 1984 Puzzle game

48. Super Mario World. 1990 Rich color, Parallax scrolling, zoom and rotate sprite.

49. Doom 1993 A landmark 1993 first-person shooter (FPS)video game by id Software.

50. Social game Happy Farm