[ODE] TriMesh
TongKe Xue
tongke at gmail.com
Wed Aug 17 14:30:02 MST 2005
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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