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Physics in games

CS 599 Physically Based Modeling for Interactive Simulation and Games Case Study: Havok Engine for Game Physics Jernej Barbic University of Southern California. Physics in games. Custom, in-house software Off-the shelf libraries Physics middleware. Physics Engines. Real-time Video games

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Physics in games

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  1. CS 599Physically Based Modeling for Interactive Simulation and GamesCase Study:Havok Engine for Game PhysicsJernej BarbicUniversity of Southern California

  2. Physics in games • Custom, in-house software • Off-the shelf libraries • Physics middleware

  3. Physics Engines • Real-time • Video games • High precision • Slow • Film • Scientific computing Half-life 2

  4. Real-time physics engines:open source • Open Dynamics Engine (ODE) • Bullet • SOFA • Vega • and several others

  5. Real-time physics engines:commercial • Havok (Ireland) (now Intel) • Physx (formerly NovodeX, now nVidia) • Vortex (Montreal) • Rubikon (Valve)

  6. Components of physics engine • Collision detection • Dynamics • rigid objects • cloth • fluids • Fracture

  7. Rigid object contact • Penalty-based • popular with soft/deformable objects • Impulse-based • Constraint-based • expensive, suitable for continuous contact

  8. Real-time simulation • Speed more important than accuracy • Objects have two representations: • Complex geometry (rendering) • Simplified geometry (collision detection, dynamics)

  9. Characters • Rag-doll physics • Rigid objects • Cloth • Controller • Natural motion(company bought by Zynga) • Particles (hair)

  10. Physics processing unit (PPU) • Dedicated physics co-processor • SPARTA and HELLAS • academic • Penn State, Univ. of Georgia • Ageia (Switzerland, 2006) • later merged into nVidia • use AGEIA's PhysX SDK

  11. GPGPU • Havok FX • was cancelled • Multi-GPU technology • AMD (CrossFireX) • nVidia (Scalable Link Interface (SLI)) • SLI just parallelizes rendering, but can dedicate a specific card just to Physx (similar to AGEIA) • Increasingly more suitable for physics

  12. Intel Larrabee • Many-core x86 • Fusion of CPU and GPU • Suitable for physics • Was scheduled for 2010, but canceled • AMD: APU (combo of CPU and GPU)

  13. Havok • Real-time commercial physics engine • Company bought by Intel (2007) ($110 million) • Used over 300 games • Halo • Half Life 2

  14. Havok Engine • Animation • Fast playback • Real-time blending • Inverse kinematics • Retargeting • AI • path-finding

  15. Havok Engine • Behavior • Character behavior development tool • Cloth • Destruction • Physics

  16. Havok Physics

  17. Havok Physics • Collision detection • Constraints • Rigid bodies • Cloth • Continuous physics Uncharted 2: Among thieves

  18. Havok Physics • Vehicle simulation • Human ragdolls • Character controller • simulate enemy characters being hit

  19. Havok Physics • Visual debugger and profiler • Content creation tools • Integration with 3rd-party renderers • 3D Studio Max • Maya

  20. Havok Physics • Extensively optimized (machine code) • Microsoft Xbox • Sony PLAYSTATION • Nintendo Wii • PC

  21. Havok Physics is not… • Simple technology • Must invest time to use it • Black box • Must understand the componentsand recombine them • Commercial renderer

  22. Havok Physics • The “Havok World” (hkpWorld) • Contains all physical objectsin the simulation • Timesteps the simulationforward in time

  23. Rigid objects • The central object in Havok • hkpRigidObject class • Add to the “world” • Set mass, inertia tensor, etc.

  24. Constraints Ball andsocket Hinge Translational

  25. Constraints

  26. Constraints

  27. Collision Detection • Broad phase and narrow phase Broadphase

  28. Collision Detection • Narrow phase • Spheres • AABBs • Cylinders • Capsules • Compound shapes

  29. Collision Detection: Queries • Closest points between two bodies • Whether two bodies penetrate • Raycast a point through spaceand get colliding objects

  30. Continuous Physics

  31. Continuous Physics • Time of impact:

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