[ODE] composite objects

[mpeniak]

Hi Guys

I hope someone is willing to help me because I cannot learn how to
redistribute mass so that the object I have created has equal mass alonog
its body. I know how to create composite object by attaching two or more
geoms to the same body and changing geoms offsets. 
I was trying to follow howto on composite objects but it did not work, I
tried it several times and it always complained about bad parameter. I also
did it when I tried to run the oringinal howto code.

Any help much appreciated:confused:
Martin

Here's me code where I have connected two geoms to the same body:

#include <ode/ode.h>
#include <drawstuff/drawstuff.h>

#ifdef _MSC_VER
#pragma warning(disable:4244 4305)  // for VC++, no precision loss
complaints
#endif

// select correct drawing functions
#ifdef dDOUBLE
#define dsDrawBox dsDrawBoxD
#define dsDrawCylinder dsDrawCylinderD
#endif

#define RADIUS 0.02	
#define BUGIE_LENGTH 0.5	
static dWorldID world;
static dSpaceID space;
static dJointGroupID contactgroup;
static dGeomID ground;
static dBodyID bugie_body;
static dGeomID bugie_geom1;
static dGeomID bugie_geom2;

// start simulation - set viewpoint

static void start()
{
  static float xyz[3] = {1.0382f,-1.0811f,1.4700f};
  static float hpr[3] = {135.0000f,-19.5000f,0.0000f};
  dsSetViewpoint (xyz,hpr);
  }

static void nearCallback (void *data, dGeomID o1, dGeomID o2)
{
  int i,n;

  // only collide things with the ground
  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 = dContactSlip1 | dContactSlip2 |
	  dContactSoftERP | dContactSoftCFM | dContactApprox1;
      contact[i].surface.mu = dInfinity;
      contact[i].surface.slip1 = 0.1;
      contact[i].surface.slip2 = 0.1;
      contact[i].surface.soft_erp = 0.5;
      contact[i].surface.soft_cfm = 0.3;
      dJointID c = dJointCreateContact (world,contactgroup,&contact[i]);
      dJointAttach (c,
		    dGeomGetBody(contact[i].geom.g1),
		    dGeomGetBody(contact[i].geom.g2));
    }
  }
}



// simulation loop
static void simLoop (int pause)
{
	  if (!pause) {
      dsSetColor (0,10,7);
      dsSetTexture (DS_WOOD);
	 
dsDrawCylinder(dGeomGetPosition(bugie_geom1),dGeomGetRotation(bugie_geom1),BUGIE_LENGTH,
RADIUS);
	  
	  dsDrawCylinder
(dGeomGetPosition(bugie_geom2),dGeomGetRotation(bugie_geom2),BUGIE_LENGTH,
RADIUS);
      
      dSpaceCollide (space,0,&nearCallback);
      dWorldStep (world,0.05);

      // remove all contact joints
      dJointGroupEmpty (contactgroup);
      }
      
}

  



int main (int argc, char **argv)
{
  // setup pointers to drawstuff callback functions
  dsFunctions fn;
  fn.version = DS_VERSION;
  fn.start = &start;
  fn.step = &simLoop;
  fn.stop = 0;
  fn.path_to_textures = "../../drawstuff/textures";
  if(argc==2)
    {
        fn.path_to_textures = argv[1];
    }



  // create world
  dInitODE();
  world = dWorldCreate();
  space = dHashSpaceCreate (0); 
  dWorldSetGravity (world,0,0,-0.5);
  ground = dCreatePlane (space,0,0,1,0);
  contactgroup = dJointGroupCreate (0);
  
// bugie body
  bugie_body = dBodyCreate (world);
  dBodySetPosition(bugie_body,0,0,0.8);
    bugie_geom1 = dCreateCylinder (space,RADIUS,BUGIE_LENGTH);
  dGeomSetBody (bugie_geom1,bugie_body);
  dGeomSetOffsetPosition(bugie_geom1,0,0,0);

  bugie_geom2 = dCreateCylinder (space,RADIUS,BUGIE_LENGTH);
  dGeomSetBody (bugie_geom2,bugie_body);
  dGeomSetOffsetPosition(bugie_geom1,0,0,0.4);
  
  dMatrix3 rotation;
  dRFromAxisAndAngle(rotation,0,2,0,0.6);
  dGeomSetOffsetRotation(bugie_geom1,rotation);
  dRFromAxisAndAngle(rotation,0,2,0,-0.6);
  dGeomSetOffsetRotation(bugie_geom2,rotation);
  dRFromAxisAndAngle(rotation,0,1,0,1.7);
  dBodySetRotation(bugie_body,rotation);
  // run simulation
  dsSimulationLoop (argc,argv,352,288,&fn);
  dWorldDestroy (world);
  dCloseODE();
  return 0;
}

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