Point inside a mesh

[peter.lapisu]

hello

iam a bit new to bullet, and using it with SIO2 on the iphone

how can i detect a point mesh collision (meaning that the point is inside the mesh)

so how do i determine if a point is inside a mesh, is there some function for this?

like checkPointInsideMesh(...)

thank you

[Ripiz]

If you've created btBvhTriangleMeshShape, you could raycast from that point, into any direction. If it hits triangle, which is backfaced (from rays perspective), then it's inside. But this assumes your models are properly made.

[peter.lapisu]

the problem is, that the returned normal, is always facing towards the ray origin, so if the point is inside a mesh and hits a face, which normal points outside, the callback returns a normal which is sadly pointing inside , so the dot of the returned normal and the ray is always negative

here is some code

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SIO2object * sio2ObjectLocationInsideMesh( SIO2physic *_SIO2physic, SIO2object * _sio2Obejct, SIO2object * p )
{
   vec3 & loc = _sio2Obejct->_SIO2transform.localspace.loc;
   
   btVector3 rayOrigin(loc.x, loc.y, loc.z);
   
   btVector3 rayTarget(0, 0, 0);
   
   btCollisionWorld::ClosestRayResultCallback collision_ray( rayOrigin, rayTarget );
   
   _SIO2physic->_btSoftRigidDynamicsWorld->rayTest( rayOrigin, rayTarget, collision_ray );
   
   if( collision_ray.hasHit() ) {

      vec3 n;      
      n.x = collision_ray.m_hitNormalWorld.x();
      n.y = collision_ray.m_hitNormalWorld.y();
      n.z = collision_ray.m_hitNormalWorld.z();
      
      vec3 rayDir;
      
      //if rayTarget is [0,0,0], we practicly dont need this, as rayDir = -loc
      sio2Vec3Diff(&v, &loc, &rayDir);
      //sio2Normalize(&rayDir, &rayDir);
      
      float dot = sio2DotProduct(&rayDir, &n);
      
      INFO_ARG("dot %f", dot);

      return ( SIO2object * )( ( btRigidBody * )collision_ray.m_collisionObject )->getUserPointer();      
   }
   
   return NULL;
}

[peter.lapisu]

ok, i can overload the

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virtual	btScalar	addSingleResult(LocalRayResult& rayResult,bool normalInWorldSpace)

and get the collision shape

Code: Select all

rayResult.m_collisionObject->getCollisionShape();

but how do i get the normal of the face which is hit?

thank you

[Ripiz]

I can't help on this one, sorry
I'm pretty new too.