3D Cloth Simulation Demonstration April 10, 1999

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v. 1.0

This is the sample application that accompanies the May 99

Game Developer magazine. It is meant as a demonstration of

a method for 3D cloth simulation in OpenGL.

Cloth simulation is a very complex process. This column and

demo just scratches the surface. It is simply a way of building

a form of cloth using the mass and spring system from last

month. It is sort of a macro function (CreateClothPatch in OGLView.cpp)

that builds all the various springs and attaches them.

There are many places it can be improved and modified.

Please read the article and check the references in the

"For Further Info" section if you are really interested

in cloth simulation.

Ideas for Optimization and expansion:

1. Change the springs to work on the Squared distance to avoid

the sqrt for each spring.

2. The collision detection really slows things down. The model

could be changed so that it didn't back up the sim for cloth->sphere

collisions. You could simply move the vertex outside the sphere.

I have tried this and it makes things a bunch faster at the expense

of some accuracy.

3. Optimize the integration code. Especially the RK4 needs some

work.

4. Add a fix to the "super-elastic" effect I described in the

article.

5. Add an implicit integrator like in the Witkin and Baraff

reference.

6. Add in cloth->box collision.

Hopefully this will get you started. If you make any

improvements send them to me and I will post them with a

credit to you.

Write to me if you have problems or questions and check

the web site or Game Developer's web site for updates.

I hope to expand on this demo some more in the future.

Jeff Lander

jeffl@darwin3d.com

www.darwin3d.com/gamedev.htm

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I compiled the code with Visual C++ 6.0. It has been tested

with Microsoft OpenGL, SGI OpenGL for Windows, Permidia 1 and 2 OpenGL

Drivers, Riva 128 (New Beta OGL Drivers), AccelGalaxy,

and Symetra Ultra FX Pro.

It should run on any OpenGL fully complient driver. This

DOES NOT include the mini-QuakeGL driver for 3DFX. 3DFX

OpenGL does not support OpenGL in a window so will not work

with this application.

Also, depending on how well GLlines are drawn on your system, the

sim should run too fast, too slow, or just right. I try to lock

it to the clock except to set the timesteps. If it is strange,

adjust COGLView::RunSim().