[ODE] TriMesh

[kurimail]

>From what i remember, you can't move the trimesh after the creation of the
data...

> Question 1: Does your Tri Mesh have a body associated with it, if not then
> it will never get in your loop.
> Question 2: How many contacts are being generated in the loop. Does the
> object just fall or does it interwine and fall?
>
> Thanks,
> Gopi
>
> -----Original Message-----
> From: TongKe Xue [mailto:tongke at gmail.com]
> Sent: Wednesday, August 17, 2005 2:30 PM
> To: ode at q12.org
> Subject: [ODE] TriMesh
>
>
> Hi,
>
>   I have this serpentine robot I'm simulating in ODE. It's just a
> bunch of boxes connected together by hinges. I'm having some problems
> with having it stay on tri-meshes (as opposed to falling through).
>
> My nearCallbackk looks like:
>
> void nearCallback (void *data, dGeomID o1, dGeomID o2)
> {
>   int i,n;
>
>   dBodyID b1 = dGeomGetBody(o1);
>   dBodyID b2 = dGeomGetBody(o2);
>
>   if (b1 && b2 && dAreConnectedExcluding(b1, b2, dJointTypeContact))
>     return;
>
>   const int N = 10;
>   dContact contact[N];
>   n = dCollide (o1,o2,N,&contact[0].geom,sizeof(dContact));
>   if (n > 0) {
>     for (i=0; i<n; i++) {
>       contact[i].surface.mode = dContactSoftERP | dContactSoftCFM|
> dContactApprox1;
>       //contact[i].surface.mode = dContactSlip1 | dContactSlip2 |
> dContactSoftERP | dContactSoftCFM| dContactApprox1;
>       contact[i].surface.mu = dInfinity;
>       contact[i].surface.soft_erp = 0.2;
>       contact[i].surface.soft_cfm = 0.001;
>       contact[i].surface.bounce = 0.01;
>       dJointID c = dJointCreateContact (G_simul_world,
> G_simul_contactgroup, contact+i);
>       dJointAttach (c,b1,b2);
>     }
>   }
> }
>
>
>   What works:
>     * snake robot does NOT fall through the floor (dPlane)
>     * snake robot does NOt fall through boxes (dBox)
>
>   However, now that I play with tri-meshes, I have the following problem:
>     * in some positions (like 0, 0, 0) if I drop the snake, it lands
>       on the trimesh, takes it's contour, and everything is good.
>     * however, if I move the tri-mesh around a bit, using
>       dGeomSetPosition, the snake will fall right through the trimesh
>
>   The entire trimesh is constructed in the same way, as follows:
>
>   for(int i=0; i<width; ++i)
>     for(int j=0; j<length; ++j)
>       locs[i][j] = some_random_value();
>   smooth(locs, window, iterations);
>
>   for(int i=0; i<width; ++i)
>     for(int j=0; j<length; ++j) {
>       vertex[i*length+j][0]=i;
>       vertex[i*length+j][1]=j;
>       vertex[i*length+j][2]=locs[i][j];
>     }
>
>   // and then I construct triangles for the following pairs:
>
>   (i, j) (i, j+1), (i+1, j)
>      and
>   (i+1, j) (i, j+1), (i+1, j+1)
>
>   for i<width-1; j<length-1;
>
>   // basically, I create a grid, and chop each square into two
>   // triangles
>
>   this Trimesh also displays properly in ODE
>
>   things I've tried:
>   * tuning the step size down to 0.001 (for time step size)
>   * tuning the CFM down to 0.000001
>
>   neither of which helped
>
>
>
>   Any ideas what might be going on?
>
> Thanks,
> --TongKe
>
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