[ODE] Step by step guide to ODE

[Pierre-Laurent CHAMBERT]

ok here's my basic stuff in my Physics module 

------------------------------------------------------------
Init :
  m_World = dWorldCreate();
  m_Space = dHashSpaceCreate(0);
  m_ContactGroup = dJointGroupCreate(0);

  // setup default world
  dWorldSetGravity(m_World, 0.0, -9.81, 0.0);
  dWorldSetCFM(m_World, 1e-5);
  dWorldSetERP(m_World, 0.8);

  dWorldSetAutoDisableFlag (m_World,1);
  dWorldSetContactMaxCorrectingVel (m_World,0.1);
  dWorldSetContactSurfaceLayer (m_World,0.001);

  // add debug plane
  m_StaticPlane = new GroundObject();
------------------------------------------------------------

------------------------------------------------------------
then to add a body + is collision shape :
  m_Body = 0;
  m_Geom = 0;

  // create a sphere, 11cm radius
  m_Body = dBodyCreate(PhysicsManager::Inst().QueryWorld());

  dMassSetSphere (&m, 0.95f, 0.11f);
  m_Geom = dCreateSphere (PhysicsManager::Inst().QuerySpace(), 0.11f);

  dBodySetMass (m_Body,&m);

  dGeomSetBody(m_Geom, m_Body);
------------------------------------------------------------

------------------------------------------------------------
next the collision callback func
 int i;
  // if (o1->body && o2->body) return;
  PhysicsManager * pm = (PhysicsManager *)data;
  // 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;

  BaseObject *obj1 = (BaseObject *)dGeomGetData(o1);
  BaseObject *obj2 = (BaseObject *)dGeomGetData(o2);

  
  //printf("%d - %d\n", obj1, obj2);
  assert(obj1 != NULL && obj2 != NULL);
  float friction = obj1->GetFriction() < obj2->GetFriction()? 
obj1->GetFriction() : obj2->GetFriction();

  dContact contact[MAX_CONTACTS];   // up to MAX_CONTACTS contacts per box-box
  for (i=0; i<MAX_CONTACTS; i++) {
    contact[i].surface.mode = dContactBounce | dContactSoftCFM | 
dContactMu2;// | dContactSlip1 | dContactSlip2;
    contact[i].surface.mu = friction;
    contact[i].surface.bounce = 0.7f;
    contact[i].surface.bounce_vel = 0.1f;
    contact[i].surface.soft_cfm = 0.01f;
  }



  if (int numc = dCollide (o1,o2,MAX_CONTACTS,&contact[0].geom, 
sizeof(dContact))) {
    for (i=0; i<numc; i++) {
      dJointID c = dJointCreateContact (pm->m_World, pm->m_ContactGroup, 
contact+i);
      dJointAttach (c,b1,b2);
    }
 
  }

friction comes from my own rigidbody class, ignore it, use a value like 
dInfinity
------------------------------------------------------------


------------------------------------------------------------
the the sim loop

void PhysicsManager::Integrate()
{
  dSpaceCollide (m_Space, this, &PhysicsManager::ODENearCallback);
  dWorldQuickStep (m_World, FixedPhysicFrameRate);
  dJointGroupEmpty (m_ContactGroup);
}


I hope this can help you :)

On Wednesday 12 July 2006 18:20, michael kapelko wrote:
> somewhere in SimLoop, but i'm lost in the code, it's TOO much for the
> beginning
> i had a look at Bounce, but it's hard either. i don't get all these
> classes, enormous amount of bodies.
> i simply want very-very basic world, space, body, second body, collision
> to get at least some clue in ODE
> thanks.
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