Game Hardware and Engines

1
Game Hardware and Engines

• J. Scott Hofmann
• Bethesda Softworks, Inc.
• shofmann_at_mindspring.com

Now at Boeing - Autometric, Inc.
2
Introduction

• Game Hardware
• History
• Examples
• Game Engines
• Definition
• Examples
• Implementation
• Game Engineering

3
Game History

• Source http//gamespot.com/gamespot/features/vide
  o/hov/p2_01.html
• 1889 Marufuku Company founded
• Changes name to Nintendo in 1951
• 1947 Tokyo Telecommunications Engineering
  Company founded
• Changes name to Sony in 1952
• 1958 Table Tennis played on an oscilloscope
• This later becomes Pong (in 1972)

4
Game History

• 1961 Spacewar developed for PDP-1
• first game implemented in software
• 1971 First arcade game shipped
• Nolan Bushnell at Nutting Associates
• 1972
• Magnavox ships the Odyssey
• first home game console

5
Game History

• 1972 Bushnell leaves Nutting to found Atari
• Pong released
• 1977
• Atari 2600 ships
• Nintendo releases first arcade game
• 1979 Milton Bradley releases Microvision
• first handheld programmable electronic game
• 1980 Activision founded
• first third-party developer

6
Game History

• 1981 IBM ships the IBM PC
• 1985 Nintendo Entertainment System released
• 1989 Nintendo Gameboy released
• 1994
• Sony PlayStation released
• Entertainment Software Rating Board (ESRB)
  established

7
Game History

• 2000
• Playstation 2 released
• 2001
• Nintendo Gameboy Advance released
• Nintendo GameCube released
• Microsoft Xbox released

8
Game Console Hardware

• Sony Playstation 2
• development done on a PSTool
• PSTool is a Linux-based workstation
• Microsoft Xbox
• development done on a PC connected to an Xbox
  Development Kit (XDK)
• Nintendo GameCube
• code-named Dolphin

9
PlayStation 2 Architecture
10
PS2 Overview

• I/O Processor (IOP)
• controllers, FireWire, and USB ports
• Emotion Engine (EE)
• Geometry calculation
• Behavior/World simulation
• some program control and housekeeping
• Graphics Synthesizer (GS)
• receives display lists from the EE
• Graphics Interface (GIF) unit mediates EE-GS
  communications

11
Emotion Engine Architecture

• CPU 300MHz MIPS III derivative
• VU Vector Unit
• GS Graphics Synthesizer

12
EE overview

• CPU FPU program control, housekeeping
• CPU FPU VU0 AI, physics simulation
• VU1 geometry processing
• More info
• http//arstechnica.com/reviews/1q00/playstation2/e
  e-1.html

13
GS Overview

• Massively parallel rendering engine
• 150MHz core processor
• 16 pixel engines
• 4MB DRAM (i.e. frame buffer)
• 75 million polygons per second
• 20 million textured lit zbuffered blended
  polygons per second
• 2.4 billiion pixels per second
• Designed for massively multipass rendering
• each frame may have 20 passes
• NTSC TV is 30 frames per second

14
Microsoft Xbox Architecture

• PC-like architecture
• Intel Pentium III 733 MHz
• NVIDIA graphics processing unit (GPU)
• GeForce3 derivative
• NVIDIA Media Communication Processor (MCP)
• sound, video, network processor
• 64MB DDR SDRAM
• Unified Memory Architecture (UMA) - No AGP or
  video memory!
• 10GB 5400RPM hard drive!!!

15
Developing for the Xbox

• Xbox Development Kit (XDK)
• Hardware modified Xbox
• includes SCSI card for DVD emulator (hard drive
  in PC)
• Software Libraries, tools for Visual Studio 6
• XDK hardware connected to PC via ethernet
• Xbox Debug Kit
• XDK minus DVD emulator
• used by QA teams (cheaper than XDK)
• Parts of DirectX 8.0
• Modified versions of Direct3D, DirectInput,
  DirectSound, Win32

16
GPU Architecture

• GeForce3 derivative
• 250MHz clock rate
• between Ti200 and Ti500 in the PC world
• Vertex and Pixel Shaders
• Apply a program to individual vertices or polygon
  fragments (pixels)
• Provides much more hardware acceleration

17
NVIDIA MCP

• Sound processing
• 256 voices over 64 channels
• Dolby Digital encoding for surround sound
• Video processing
• MPEG-2 decoding
• used also for DVD playback
• Network processing
• 10/100-base-T ethernet

18
Comparing the PS2 and Xbox

• PS2 Massively Multipass
• Xbox Only a few passes required
• 2-3 passes per frame vs 20-30 passes per frame
• Xbox 10 million polygons per second
• 125 million polys/sec theoretical peak
• PS2 20 million polys/sec
• 75 million polys/sec theoretical peak
• Poly counts are per pass!
• Xbox 10M / 3 passes 3.3M polys per frame
• PS2 20M / 20 passes 1M polys per frame

19
GameCube Architecture

• 485MHz IBM PowerPC 750CXe CPU
• equivalent to a 700MHz Pentium III
• 24MB fast 1T-SRAM
• 16MB slower DRAM
• 162MHz ArtX (now ATI) GPU
• 2MB 1T-SRAM as zbuffer
• 1MB 1T-SRAM as texture cache

20
GameCube MCP

• Macronix DSP provides sound
• Not powerful enough for Dolby Digital
• Dolby Pro Logic II possible instead
• Network adapter not included
• optional peripheral
• DVD playback not included
• possible in Matsushita device

21
Game Engines

• Control the presentation of game content
• Geometry and Texture
• Script
• Sound
• Simulation (i.e. Physics)
• AI
• Network Traffic

22
Engine Architecture
Game Content
Geometry Management
Animation and Simulation
Sound
Script Interpreter
Network
Core Library
23
Core Library

• Math
• Range-checked Trigonometric functions
• Linear Algebra
• Vector, Matrix, Quaternion
• Curves and Surfaces
• Linear, Quadratic, and Cubic curves
• Bezier and Tension-Continuity-Bias (TCB) curves
• Bezier and Subdivision Surfaces

24
Core Library

• Bounding Volumes
• Box and Sphere
• Intersection testing
• Memory Management
• Leak detection
• Reference counting and/or garbage collection
• Error Reporting
• Miscellaneous Types

25
Geometry Management

• Move as many polygons as possible as quickly as
  possible
• Apply Texture (usually multiple textures)
• Lighting
• Color and Blending
• Depth sort (ZBuffer, BSP tree)
• Bind shader programs (DX8)
• Control each rendering pass
• Cull out invisible geometry

26
Geometry Management

• Meshes are exported from the art tool
• Usually 3D Studio MAX or Maya
• Some additional processing is done
• Level-of-detail simplification
• Polygons organized into engine-friendly
  structures
• Vertex arrays
• Triangle strips
• Scene graph
• Texture compression
• Colors checked for illegal values
• Important if the display is a TV

27
Vertex Arrays

• Vertex Buffers (DX) / Vertex Arrays (OGL)
• An array of per-vertex information
• x, y, z position
• r, g, b color
• i, j, k normal (for lighting and physics)
• u, v, w texture (w optional)
• Multitexturing would append other (u, v, w)
  coordinates
• Other stuff (tangent, binormal for bump mapping
  other application-specific per-vertex information)

28
Vertex Arrays

• Each array has a primitive type
• Points
• Lines
• Triangles
• Triangle Strip or Fan
• Quadrilaterals
• Quad strip
• Polygons

29
Triangle and Quad Strips

• Reduce the number of redundant vertex
  specifications
• Reduces the function-call overhead
• Vertices transformed only once
• More efficient use of bus bandwidth

30
Triangle Stripping

• Triangle strips can be created from an arbitrary
  triangle mesh
• generating optimal strips is NP-hard
• Usually done by a noninteractive tool

31
Render State Management

• Minimize the number of state changes
• Enable/disable lights
• Change textures
• Enable/disable blending
• Geometry organized to batch similar polygons
• Scene graph and/or display lists built

32
Scene Graph

• Directed Graph structure
• Used for scene-database management
• includes culling and interaction support
• graph traversal paramount for speed
• OpenInventor, VRML, Fly3D (in book)

33
Scene Graph
34
Display Lists

• Basic support for scene-database management
• Store a list of render commands in an optimized
  fashion
• Display lists are immutable once created
• OpenGL called display lists
• Also compiled vertex arrays
• Direct3D part of the vertex buffer

35
Culling

• Select what geometry should be drawn
• Three kinds of culling
• Frustum culling
• Occlusion culling
• Detail culling
• Culling algorithms use bounding volumes (BVs)
• The actual polygon mesh is too big
• Also useful for collision detection

36
Bounding Volumes

• Oriented Bounding Boxes (OBB)
• Axis-Aligned Bounding Boxes (AABB) a subset
• slow, but usually the tightest bound
• Bounding Spheres
• fastest intersection tests
• lots of wasted space, which causes false positive
  tests
• Bounding Capsules
• middle ground between OBBs and Bounding Spheres

37
Hierarchical Bounding Volumes

• Tree of bounding volumes
• Parent nodes volume encloses child node volumes
• Leaf nodes are actual geometry
• Usually built using boxes or spheres

38
Frustum Culling

• Walk bounding volume tree, testing each BV for
  intersection with frustum
• For static scenes, a spatial data structure is
  faster than the BV tree
• octtree or BSP tree best
• for dynamic scenes, data structure management
  swamps culling speedup

39
Backface Culling

• A simple form of occlusion culling
• remove all polygons which face away from the eye
• Usually done by calculating the winding order of
  a polygon
• Mirroring transforms can flip this order
• Acceleration through normal masks
• sort polygons into clusters by normal vector
• test each cluster once for culling

40
Occlusion Culling

• Remove geometry in the camera frustum but not
  visible
• Difficult to do
• Portals
• Research still being done
• Hierarchical Z-Buffer
• Occlusion Masks
• Shadow volume culling

41
Portals

• Divide indoor scene into convex cells connected
  by portals
• Build cell graph from this representation

42
Portals

• What is rendered is then determined by querying
  the cell graph
• cell identified containing eye point
• That cell is rendered
• For each portal, that portal is projected onto
  the view plane
• if portals projection is non-empty, recursively
  render that cell

43
Detail Culling

• Select the appropriate number of polygons to
  display
• view-independent criteria
• per-frame polygon count
• arbitrary number picked by developer
• view-dependent criteria
• size of screen projection
• distance from eye

44
Static Level-of-Detail

• Pre-generate a fixed number of reduced-polygon-cou
  nt meshes
• Switch between meshes at runtime
• view-independent polygon count caps
• view-dependent remove redundant detail
• Morph between meshes
• eliminates popping artifacts during the switch

45
Continuous Level-of-Detail

• Precalculate a sequence of vertex splits or edge
  collapses to generate a LOD level at runtime

46
Image-based Rendering

• Textures with pre-rendered images are used to
  replace overly complex geometry
• Billboards
• screen- or world-aligned polygons
• used for trees, smoke, explosions, etc.
• Impostors (aka sprites)
• Polygons containing images of complex scenes
• Regenerated when the eye moves beyond threshold

47
Animation

• Rigid Body Animation
• Controlling a meshs position and orientation
• TCB curves used
• Soft Body Deformation
• Character Animation
• 3D Studio MAXs Physique plugin
• Freeform Deformation

48
Character Animation

• Create a hierarchy of bones
• Bones are usually scene-graph nodes
• The bones are then animated
• Rigid-body animation
• Skin animation derived from the bone animation

49
Character Animation
50
Simulation

• Physics Simulation
• Behavior Simulation
• Often part of AI
• For each frame
• Calculate Motion
• Apply Constraints (e.g. collision detection)
• Apply Motion to Geometry
• Draw Frame

51
Collision Detection

• Necessary for realistic gameplay
• Prevent walking through walls, other objects
• Used by most dynamics algorithms
• Two phases
• Collision Detection
• Does one object intersect another?
• Collision Resolution
• Given two intersecting objects, what should
  happen?
• Bounding Volumes used here

52
Sound

• Platform-specific APIs used
• 3D audio
• Sounds are part of the scene graph
• Each sound has a geometric location
• Occlusion, attenuation, doppler shifting
• Dolby Pro Logic and Dolby Digital
• 5.1 channels
• 2 main, center, 2 rear surround, subwoofer

53
Network

• Manage network connections
• Connect to game server
• Battle.net, MSN Game Zone
• LAN play
• Peer-to-peer
• Synchronize game clients
• Game world is a distributed database
• Scene graph derived from game world

54
Script Interpreter

• Game content implemented through scripts
• When this door opens, summon monster
• UnrealScript, QuakeC
• Scripts are usually interpreted
• Scripts are compiled to bytecodes
• More engines are now using the Java VM

55
Game Content

• What the player sees and does
• Art, sound, scripts
• Usually not developed by the programmers
• Programmers provide engine and technology

56
Game Development

• Game Team Composition
• Management
• Programmers
• Software Development
• Content Developers
• Game Play
• Script Development
• Artists
• Graphics and Sound

57
Conclusion

• Game hardware changes every 3-5 years
• NES - SNES - N64 - GameCube
• PlayStation - PlayStation2
• Usually no backwards compatibility
• PC software - Voodoo - GeForce -GeForce3
• When hardware changes, the engine must change
• Hardware transformation lighting (TL)
• Programmable geometry
• Networks