/* This function dynamically adds the collision shape of another controller to
* the current controller shape provided it is a compound shape.
* The idea is that dynamic parenting on a compound object will dynamically extend the shape
*/
void KX_BulletPhysicsController::AddCompoundChild(KX_IPhysicsController* child)
{
if (child == NULL || !IsCompound())
return;
// other controller must be a bullet controller too
// verify that body and shape exist and match
KX_BulletPhysicsController* childCtrl = dynamic_cast<KX_BulletPhysicsController*>(child);
btRigidBody* rootBody = GetRigidBody();
btRigidBody* childBody = childCtrl->GetRigidBody();
if (!rootBody || !childBody)
return;
const btCollisionShape* rootShape = rootBody->getCollisionShape();
const btCollisionShape* childShape = childBody->getCollisionShape();
if (!rootShape ||
!childShape ||
rootShape->getShapeType() != COMPOUND_SHAPE_PROXYTYPE ||
childShape->getShapeType() == COMPOUND_SHAPE_PROXYTYPE)
return;
btCompoundShape* compoundShape = (btCompoundShape*)rootShape;
// compute relative transformation between parent and child
btTransform rootTrans;
btTransform childTrans;
rootBody->getMotionState()->getWorldTransform(rootTrans);
childBody->getMotionState()->getWorldTransform(childTrans);
btVector3 rootScale = rootShape->getLocalScaling();
rootScale[0] = 1.0/rootScale[0];
rootScale[1] = 1.0/rootScale[1];
rootScale[2] = 1.0/rootScale[2];
// relative scale = child_scale/parent_scale
btVector3 relativeScale = childShape->getLocalScaling()*rootScale;
btMatrix3x3 rootRotInverse = rootTrans.getBasis().transpose();
// relative pos = parent_rot^-1 * ((parent_pos-child_pos)/parent_scale)
btVector3 relativePos = rootRotInverse*((childTrans.getOrigin()-rootTrans.getOrigin())*rootScale);
// relative rot = parent_rot^-1 * child_rot
btMatrix3x3 relativeRot = rootRotInverse*childTrans.getBasis();
// create a proxy shape info to store the transformation
CcdShapeConstructionInfo* proxyShapeInfo = new CcdShapeConstructionInfo();
// store the transformation to this object shapeinfo
proxyShapeInfo->m_childTrans.setOrigin(relativePos);
proxyShapeInfo->m_childTrans.setBasis(relativeRot);
proxyShapeInfo->m_childScale.setValue(relativeScale[0], relativeScale[1], relativeScale[2]);
// we will need this to make sure that we remove the right proxy later when unparenting
proxyShapeInfo->m_userData = childCtrl;
proxyShapeInfo->SetProxy(childCtrl->GetShapeInfo()->AddRef());
// add to parent compound shapeinfo (increments ref count)
GetShapeInfo()->AddShape(proxyShapeInfo);
// create new bullet collision shape from the object shapeinfo and set scaling
btCollisionShape* newChildShape = proxyShapeInfo->CreateBulletShape(childCtrl->GetMargin(), childCtrl->getConstructionInfo().m_bGimpact, true);
newChildShape->setLocalScaling(relativeScale);
// add bullet collision shape to parent compound collision shape
compoundShape->addChildShape(proxyShapeInfo->m_childTrans,newChildShape);
// proxyShapeInfo is not needed anymore, release it
proxyShapeInfo->Release();
// remember we created this shape
childCtrl->m_bulletChildShape = newChildShape;
// recompute inertia of parent
if (!rootBody->isStaticOrKinematicObject())
{
btVector3 localInertia;
float mass = 1.f/rootBody->getInvMass();
compoundShape->calculateLocalInertia(mass,localInertia);
rootBody->setMassProps(mass,localInertia);
}
// must update the broadphase cache,
GetPhysicsEnvironment()->refreshCcdPhysicsController(this);
// remove the children
GetPhysicsEnvironment()->disableCcdPhysicsController(childCtrl);
}
