Physics

Michael Vernier

Robert Weekley

Michael Ford

Why Physics?

• More interactivity

• Looks cool (explosions)

• More realistic

• More variety and easier animations (rag doll physics for death animations)

• Better gameplay (space fighter, driving games)

Why a Physics Engine?

• Physics simulation is hard

• Requires very stable integrator

• Articulated bodies especially take difficult math

• Optimization is important

• Spring systems explode easily

Major Features

• Collision detection

• Newtonian forces and collision response

• Buoyant forces

• Friction

• Articulation and jointed characters (rag doll)

• Prebuilt objects for simulation

Physics Toolkits

• ODE (Open Dynamics Engine)• Ageia PhysX• Newton Game Dynamics• Havok• Havok FX• Tokamak Game Physics

Newton Game Dynamics

• Free for use with credit to authors.

• Cross Platform (Win32, Mac OS X, Linux)

Features

• Collision Detection• Collision Response• Buoyancy• Friction• Seven different Joints• Rag Doll Physics• Height Map Collision• Claims very stable solver

API

• C++ API

• Tutorials

• Wiki

• API Documentation seems complete

Used In

• Not very much yet.

• Several small independent games.– Future Pinball– Trembling Towers– Classic Cars Racer– Virtual Reality Chat– Ultra Stein 3D Pinball

Ageia PhysX

• Features– Designed for massively parallel hardware– Designed with games in mind

• Complex rigid body system• Volumetric fluid and cloth simulations• Advanced Character Control• Ray-cast vehicles

– Support for many scenes

Ageia PhysX

• Features (cont’d)– Remote debugging capability– Cross-Platform

• Single and multi-core PC• Xbox 360• Playstation 3• PhysX Processor!

Ageia PhysX

• Problems– Commercial licensing

• Free for non-commercial projects• $50k per SKU for commercial products

– Currently no killer game to show off the processor

• But, they’re on their way

– Limited availability of PhysX cards

Ageia PhysX

• Who’s using PhysX?– Partners

– Other Developers

Ageia PhysX

• API – C++– Primitives

• Box (AABB, OBB), sphere, capsule, plane, line, ray, height map, convex mesh, triangular mesh

– Joints• Spherical, revolute, prismatic, cylindrical, fixed,

distance, point in plane, point on line, pulley, 6DOF

Ageia PhysX

• Tools– PhysX Create

• Plugins for 3DS Max and Maya

– PhysX Rocket• Preview and tuning of content

– PhysX VRD• Real-time visual remote debugger

Ageia PhysX

• Demos– GRAW comparison of PhysX processor– Fluid Dynamics (Fog, Napalm)– Artificial Studios Cellfactor– Bet on Soldier: Blood Sport

Open Dynamics Engine (ODE)

• Rob needs to get off his lazy butt and fill this in

Wunderverbindungen

Open Dynamics Engine (ODE)

• Features– Open Source– Platform independent– Rigid Body Dynamics (V3)

• Vehicles• Virtual Reality Environments• Virtual Creatures

Open Dynamics Engine (ODE)

• Features (cont’d)– Collision Detection– Collision Handling– Friction– Three different Joints

Open Dynamics Engine (ODE)

• Problems– Traded Accuracy for Speed and Stability– 2 Years since last release – 2 + Months since last “Nightly Build”– Samples crash or don’t work

Open Dynamics Engine (ODE)

• Who’s using ODE?– 87 linked users– Games & Game Engines

• 3Impact• Gryps Engine

– Tools• Juice• Blender

– Simulators

Havok

• Industry Standard

• Used in Half Life 2, Halo 2, F.E.A.R., and many other blockbuster games.

• Also used in the Jupiter EX game engine.

• Very expensive (they won’t even give you a price if you don’t work for EA)

• Joining with nVidia to use the GPU for physics calculations.

Physics and Ogre

• OgreODE– Adds prefab vehicles and rag-doll support

• OgreNewt– Implements nearly all of Newton’s

functionality

• NxOgre– Adds state machine support

Questions?