cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   Anthony
   Member

   I am using Gray Olson's bullet wrapper to incorporate physics in my Cocos3d project. I am trying to "attach" a CC3MeshNode to a btRigidBody. I am having troubles getting the rotation of the CC3MeshNode to match up with the rotation of the btRigidBody. Here is my code:

   -(void) initializeWorld

   CC3PODResourceNode* podRezNode = [CC3PODResourceNode nodeFromResourceFile: @"DieCube.pod"];
   dieMesh = (CC3MeshNode*)[podRezNode getNodeNamed: @"Cube"];
   dieMesh.isTouchEnabled = YES;
   [self addChild:dieMesh];
    btCollisionShape *dieShape = new btBoxShape(btVector3(1.0, 1.0, 1.0));
   btDefaultMotionState *fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(0, 0, 0)));
    btScalar mass = 1;
   btVector3 fallInertia(0, 0, 0);
   dieShape->calculateLocalInertia(mass, fallInertia);
    btRigidBody::btRigidBodyConstructionInfo dieRigidBodyCI(mass,fallMotionState,dieShape,fallInertia);
   dieRigidBodyCI.m_restitution = 0.1;
   dieRigidBody = new btRigidBody(dieRigidBodyCI);
   dieRigidBody->setDamping(0.3, 0.8);
   dynamicsWorld->addRigidBody(dieRigidBody);
   [[CCScheduler sharedScheduler] scheduleSelector:@selector(updatePh ysics:) forTarget:self interval:0 paused:NO];
   reset = NO;
   left = true;
   steps = 0;

   -(void) updatePhysics:(ccTime)dt

   dynamicsWorld->stepSimulation(1/60.f, 10);
   dynamicsWorld->debugDrawWorld();
    btTransform trans;
   dieRigidBody->getMotionState()->getWorldTransform(trans);
   btVector3 dieRBPos = trans.getOrigin();
   float velX = dieRigidBody->getLinearVelocity().x();
   float velY = dieRigidBody->getLinearVelocity().y();
   float velL = dieRigidBody->getLinearVelocity().length();
    	if (dieRigidBody->getLinearVelocity().length() > -0.1 && dieRigidBody->getLinearVelocity().length() < 0.1 && !reset) {
            LogInfo(@"Linear X is %f, linear Y is %f, linear length is %f", velX, velY, velL);
    		if(left) {
               dieRigidBody->applyImpulse(btVector3(-3,0,4), btVector3(dieRBPos.getX(), dieRBPos.getY(), dieRBPos.getZ()));
   			left = false;
   			reset = true;
   		} else {
               dieRigidBody->applyImpulse(btVector3(3,0,4), btVector3(dieRBPos.getX(), dieRBPos.getY(), dieRBPos.getZ()));
   			left = true;
   			reset = true;
   		}
   	}
    dieMesh.location = cc3v(trans.getOrigin().getX(), trans.getOrigin().getY(), trans.getOrigin().getZ());
   btQuaternion quat = trans.getRotation();
   btVector3 rotAxis = quat.getAxis();
   // dieMesh.rotation

   I can get the location of dieMesh to match up with dieRigidBody, but I am not sure how to update the rotation of the dieMesh to match that of the dieRigidBody. Anybody have an idea?

   Posted 3 months ago #
2. 

   Anthony
   Member

   Well I tried this code, and my dice is rotating, but not properly:

   dieMesh.location = cc3v(trans.getOrigin().getX(), trans.getOrigin().getY(), trans.getOrigin().getZ());
   
       btQuaternion quat = trans.getRotation();
       CC3Vector vec;
       vec.x = quat.getX();
       vec.y = quat.getY();
       vec.z = quat.getZ();
   
       [dieMesh rotateByAngle:(quat.getW()) aroundAxis:vec];

   and I also tried this, but the dice rotates uncontrollably:

   [dieMesh rotateByQuaternion:(CC3Vector4Make(quat.getX(), quat.getY(), quat.getZ(), quat.getW()))];

   Does anyone see what I'm doing wrong?

   Posted 3 months ago #
3. 

   Anthony
   Member

   OK, sorry for spamming the thread but I think I am on the right track. I've been using this code:

   dieMesh.quaternion = CC3Vector4Make(trans.getRotation().getX(), trans.getRotation().getY(), trans.getRotation().getZ(), trans.getRotation().getW());

   is this the proper (best) way to match the rotation of the CC3Node to the btRigidBody? Because the rotation doesn't seem to match up properly (sometimes the dice will land and stabilize on a corner).

   Posted 3 months ago #
4. 

   Anthony
   Member

   No one has any ideas why the rotations aren't matching up?

   Posted 3 months ago #
5. 

   dutchiedave
   Member

   I know this is a old thread but i have been bashing my head against the same problem, so hopefully it helps someone else. The solution as far as i can tell is:

   `dieMesh.quaternion = CC3Vector4Make(trans.getRotation().getW(), trans.getRotation().getX(), trans.getRotation().getY(), trans.getRotation().getZ());'

   Notice the position of the W component.

   Dave.

   Posted 1 month ago #

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