havok. ©copyright 2006 havok.com (or its licensors). all rights reserved. havokfx next gen physics...

Havok. ©Copyright 2006 Havok.com (or its licensors). All Rights Reserved.

HavokFXNext Gen Physics on ATI GPUs

Andrew Bowell – Senior Engineer

Peter Kipfer – Senior Engineer


Why use physics in games?

A brief history of the Havok SDK Havok 1

Large feature set; rigid bodies, cloth, rope, soft bodies, water, particles

Havok 2 Rigid body physics for the PS2 generation

Havok 3 Ultra realistic physics

Havok 4 Next-gen physics


What is “next gen” physics?

Gameplay physics

Fx physics

Performance

Performance

Performance

Performance

Performance

Quality

Customization

Controllability


What is FX physics?

Physics based effects on a massive scale 1,000s to 10,000s of objects– Rigid bodies– Particles– Fluids– Cloth– and more to come

Running on PC and consoles (Xbox 360, PS3)


Why use the GPU?

The GPU is a next-gen platform– Can be thought of as a 1000

multiprocessor machine

It is unbelievably fast when given the right task– Rendering, for example

Huge existing install base of graphics cards capable of running GPU physics


Havok and ATI

Strong partnership Working specifically on HavokFX in the run up to its showcase on ATI at Computex 2006

Best Innovation – Computex 2006 [Hexus]


How does the GPU work?

GPUs are very powerful data parallel processors– 1000 simultaneous threads– Very high memory bandwidth– 1 cycle latency per instruction– Can execute up to 4 instructions per cycle

ATI X1900 XTX– 48 pixel processors– Over 350 GFLOPS

Issues– Normally only up to 16 float outputs in SM3.0– Limited inputs too


Demo Set 1


Solve Collision

sIntegrate Collide

Ballistic physics refresher course


Find overlapping pairsIntegrate


Narrow phase collide


Solve collisions


Solve Collision

sIntegrate Collide

Is physics a data parallel task?

Anatomy of a clock tick



Step Body 1

Step Body 2

Step Body 1000

Integrate

New Positions

Position&

Velocity


Solve Collision

s

Integrate

Collide





Find pairs

Collide Pair 1

Collide Pair 2

Collide Pair 4000

Collide

ContactsNewPositions


Solve Collision

sIntegrate Collide





Solve Collisions

NewVelocities

Contacts&

Velocities

Body 1

Body 2

Body 5

Body 7

Body 6

Body 3 Body 8

Body 4

1

23

4

5

6

7

8 910

11

12



Solve Collisions

NewVelocities

Contacts&

Velocities

Body 1

Body 2

Body 5

Body 7

Body 6

Body 3 Body 8

Body 4



Solve Collisions

NewVelocities

Contacts

Solve link 1

Solve link 2

Solve link

1200

Solve link 1

Solve link 2

Solve link 1000

Solve link 1

Solve link 2

Solve link 800

Batch 1 Batch 2 Batch 3


Solve Collision

sIntegrate Collide

Physics is a data parallel task

100% data parallel

80% data parallel

95% data parallel


Havok Fx Features Overview

FX Rigid Bodies– Convex collision bodies– Simple stable stacking

FX Particles– Inelastic particle-particle collisions– Fluid effects– Cloth

Lightweight framework

Fully integrated with Havok 4.0– Everything collides with everything else


FX Particles

Particles are like simple rigid bodies

Much faster to simulate and render– One vertex per particle (point sprites)

Havok FX particle framework gives you– Particle-particle collisions– Particle-rigid body collisions– User-defined behaviours and emitters


FX Behaviors and Emitters

Executed on GPU Uses SM3.0, e.g. HLSL

Alter velocities and positions– Wind, gravity

Per object user data – for custom properties


Integrated Toolchain

Leverages Havok physics exporters and tools pipeline


Preview and Pipeline


Simple behaviors

GPU Memory

Positions

Velocities

CPU Memor

y

Readback from GPUWrite back to GPUModify on CPU


GPU Memory

Positions Textures

Game play physics interaction

CPU Memory

Rigid Bodies

Collision shapes

Velocities Textures

Collision Shapes Textures

Game play physics FX physics

Once perSimulation

Once perFrame


Demo Set 2


Rendering and CrossFire

Rendering needs careful consideration!– Most renderers will not render 20K objects well– Must use custom / vendor techniques

Havok FX returns handle to vertex buffers– Current rigid body transforms– Current particle positions– Optionally other particle / body state useful for

rendering

The future is multiple GPUs


Dual and Triple GPU Physics

Second (or third) GPU can be used for graphics or physics simulation, or share the primary card


FX Rigid Bodies again

We said the GPU was fast…


Future of Havok FX

Distributing physics across multiple GPUs– e.g. 2 GPUs for physics, 2 for rendering

Brittle fractureAdvanced smoke/cloud rendering– Volumetric shadowing

Advanced fluids– Smoothed particle hydrodynamics– Isosurface extraction using DirectX 10

Geometry Shader


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