[ODE] Friction problems & Donating Sample Code to ODE

[David Whittaker]

I don't see anything wrong with your collision code, maybe it's skimming
just above the ground instead of slipping like it would on ice.  I'd be
more than happy to take a look at your source code and see what I can find
if you want to email it to me privately.  Russ is the guy to talk to about
contributing the code to the project.

David

> Friction Problems
> ==================
> I am working on some code to evolve a neural network to control the
> movements of a simple dog like body. Unfortunately, it looks like I
> might be having some difficulties with friction, as the best evolved
> creature looks like he is trying to move on an ice rink!
>
> I am using the piece of code below for the CD, which I grabbed from one
> of the examples. I had thought that setting surface.mu = dInfinity would
> have worked, but it doesn't seem to be doing what I want it to. To be
> honest, I don't know all the physics that well and I was hoping that
> maybe someone might know how I can get over this problem. (Code Below)
>
> Donating Sample Code to ODE project
> ===================================
> Ironically, I had problems putting this model together in CM Labs,
> Vortex; there were some major instabilities that I couldn't get worked
> out and tech support has been looking at it for a week now without much
> luck apparently. Kudos to ODE, since I think I am pretty close to
> getting this working in only a couple of days, and thanks for everyone
> for their help so far.  Anyway, this is a project for a grad course I am
> doing and I am basically generating a life-like skeleton to put an
> "implicit surface" in order to get a nice life-like body. Anyway, I was
> wondering if there was someone I could donate this code to, for the ODE
> project once everything is worked out (I am almost done). Basically, the
> code creates a dog like creature and evolves the weights of a neural
> network to get it to move. I thought it might be useful for anyone
> interested in doing virtual creature modeling.
>
>
> /** Code I am using for CD **/
> static void nearCallback (void *data, dGeomID o1, dGeomID o2)
> {
>     int i;
>     // exit without doing anything if the two bodies are connected by a
> joint
>     dBodyID b1 = dGeomGetBody(o1);
>     dBodyID b2 = dGeomGetBody(o2);
>     if (b1 && b2 && dAreConnectedExcluding (b1,b2,dJointTypeContact))  {
>   return;
>     }
>
>     dContact contact[4];			// up to 4 contacts per
> box-box
>     for (i=0; i<4; i++) {
>         contact[i].surface.mode = dContactBounce | dContactSoftCFM;
> contact[i].surface.mu = dInfinity;
>         contact[i].surface.mu2 = dInfinity;
>         contact[i].surface.bounce = 0.1;
>         contact[i].surface.bounce_vel = 0.1;
>         contact[i].surface.soft_cfm = 0.01;
>     }
>     if (int numc = dCollide (o1,o2,4,&contact[0].geom,sizeof(dContact)))
> {
>         dMatrix3 RI;
>         dRSetIdentity (RI);
>         const dReal ss[3] = {0.02,0.02,0.02};
>         for (i=0; i<numc; i++) {
>             dJointID c = dJointCreateContact
> (world,contactgroup,contact+i);
>             dJointAttach (c,b1,b2);
>         }
>     }
> }
>
>
> ==============================
> Rob Leclerc
> University of Calgary
> Department of Computer Science
> Office: ICT 728
> ==============================
>
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