Collision detection

[Ivan Mandić]

Hello.
I'm using NewtonGD as physics engine,what function can I use to check collision?
p.s.
I did found NewtonCollisionCollide function,but if I'm right it's made for those who aren't fully using NewtonGD.

Thanks.

[JernejL]

Use newtonupdate() it'll do collision detection and response automaticly, just use the forcetorque callback to add forces to bodies so the simulation will move.

[Ivan Mandić]

I know all that,that isn't the problem. I want to check collision for specific body after calling NewtonUpdate.?
(There is no point in using NewtonCollisionCollide if NewtonUpdate already calculated all that. )

[Julio Jerez]

In older version of Newton you can use queues to place bodies from a callback,
with newer version you can iterates over the contacts, materials, or joint from almost any objects

to find the contcat joint on a body you can use NewtonBodyGetFirstContactJoint(body)
here is an example tha will show the contact points (from the SDK)

Code: Select all

void ShowContacts (const NewtonJoint* contactJoint)
{
   // the application can implement some kind of contact debug here
   if (showContacts) {
      NewtonWorld* world;

      world = NewtonBodyGetWorld(NewtonJointGetBody0(contactJoint));
      NewtonWorldCriticalSectionLock(world);
      for (void* contact = NewtonContactJointGetFirstContact (contactJoint); contact; contact = NewtonContactJointGetNextContact (contactJoint, contact)) {
         dVector point;
         dVector normal;   

         NewtonMaterial* material;

         material = NewtonContactGetMaterial (contact);
         NewtonMaterialGetContactPositionAndNormal (material, &point.m_x, &normal.m_x);

         // if we are display debug info we need to block other threads from writing the data at the same time
         DebugDrawContact (point, normal);
      }
      NewtonWorldCriticalSectionUnlock(world);
   }
}

void ShowBodyContacts (const NewtonBody* body)
{
   // iterate over all of the contact joint for this body
   for (NewtonJoint* contactJoint = NewtonBodyGetFirstContactJoint (body); contactJoint; contactJoint = NewtonBodyGetNextContactJoint (body, contactJoint)) {
      // for debug purpose show the contact
      ShowContacts (contactJoint);
   }
}

for find when the body collide for the first time you can use struture to keep track when the body adquired contact joints and when the body loses its contact joints.

[Ivan Mandić]

Thanks man.

[JernejL]

Ah, the question wasn't clear, in that case you can use the material callback as Julio described

Just remember to assign it to bodies first using NewtonMaterialSetCollisionCallback.