Real-Time Physics Simulation Forum

Posted: **Sun Nov 17, 2013 5:32 pm**

Hey guys,

I have made a compound shape

compound = new btCompoundShape();

Then I have a collision shape added to the compound:

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btCollisionShape* turretShape = new btBoxShape(btVector3(0.4f, 0.2f, 1.2f));
btTransform turretTrans;
turretTrans.setIdentity();
turretTrans.setOrigin(btVector3(0.0f, 2.2f, 0.0f));
compound->addChildShape(turretTrans, turretShape);

The compund shape is then transformed into a rigid body and then added to a vehicle raycaster as a chassis:

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m_carChassis = CreateRigidBody(2000, tr, compound);
m_vehicle = new btRaycastVehicle(m_tuning, m_carChassis, m_vehicleRayCaster);

The vehicle is moving along, together with it's wheels, chassis and turret, but I cannot seem to get hold of the updated turret transform.
Whenever I try something like this:

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compound->getChildTransform(1).getOpenGLMatrix(mturret);

I always get the initial position of the turret, where it was first created.

Now, for the wheels I can do this:

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m_vehicle->getWheelInfo(i).m_worldTransform.getOpenGLMatrix(mwheel);

And for the chassis I can do this:

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m_vehicle->getChassisWorldTransform().getOpenGLMatrix(mchassis);

But I don't know how do I get hold of that turret collision shape updated transform?

Please note that where I need this information I have access to both the compound and the turretShape (the actual btCollisionShape).

EDIT:

I found the answer. Here's what I did:

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	btTransform chassisMatrix = m_vehicle->getChassisWorldTransform();
	btTransform turretMatrix = compound->getChildTransform(1);
	turretMatrix *= chassisMatrix;
	turretMatrix.getOpenGLMatrix(mturret);

Real-Time Physics Simulation Forum

get btCollisionShape current transform

get btCollisionShape current transform