Fix issues with btCompoundShape when adding/removing child shapes after construction of a btRigidBody.

Thanks tp for the report:
http://bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=2925&p=11700#p11700

src/BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.cpp

@@ -33,6 +33,19 @@ m_sharedManifold(ci.m_manifold)
 	assert (colObj->getCollisionShape()->isCompound());
 	
 	btCompoundShape* compoundShape = static_cast<btCompoundShape*>(colObj->getCollisionShape());
+	m_compoundShapeRevision = compoundShape->getUpdateRevision();
+	
+	preallocateChildAlgorithms(body0,body1);
+}
+
+void	btCompoundCollisionAlgorithm::preallocateChildAlgorithms(btCollisionObject* body0,btCollisionObject* body1)
+{
+	btCollisionObject* colObj = m_isSwapped? body1 : body0;
+	btCollisionObject* otherObj = m_isSwapped? body0 : body1;
+	assert (colObj->getCollisionShape()->isCompound());
+	
+	btCompoundShape* compoundShape = static_cast<btCompoundShape*>(colObj->getCollisionShape());
+
 	int numChildren = compoundShape->getNumChildShapes();
 	int i;
 	
@@ -47,14 +60,13 @@ m_sharedManifold(ci.m_manifold)
 			btCollisionShape* tmpShape = colObj->getCollisionShape();
 			btCollisionShape* childShape = compoundShape->getChildShape(i);
 			colObj->internalSetTemporaryCollisionShape( childShape );
-			m_childCollisionAlgorithms[i] = ci.m_dispatcher1->findAlgorithm(colObj,otherObj,m_sharedManifold);
+			m_childCollisionAlgorithms[i] = m_dispatcher->findAlgorithm(colObj,otherObj,m_sharedManifold);
 			colObj->internalSetTemporaryCollisionShape( tmpShape );
 		}
 	}
 }
 
-
+void	btCompoundCollisionAlgorithm::removeChildAlgorithms()
-btCompoundCollisionAlgorithm::~btCompoundCollisionAlgorithm()
 {
 	int numChildren = m_childCollisionAlgorithms.size();
 	int i;
@@ -68,6 +80,11 @@ btCompoundCollisionAlgorithm::~btCompoundCollisionAlgorithm()
 	}
 }
 
+btCompoundCollisionAlgorithm::~btCompoundCollisionAlgorithm()
+{
+	removeChildAlgorithms();
+}
+
 
 
 
@@ -168,9 +185,22 @@ void btCompoundCollisionAlgorithm::processCollision (btCollisionObject* body0,bt
 	btCollisionObject* colObj = m_isSwapped? body1 : body0;
 	btCollisionObject* otherObj = m_isSwapped? body0 : body1;
 
+	
+
 	assert (colObj->getCollisionShape()->isCompound());
 	btCompoundShape* compoundShape = static_cast<btCompoundShape*>(colObj->getCollisionShape());
 
+	///btCompoundShape might have changed:
+	////make sure the internal child collision algorithm caches are still valid
+	if (compoundShape->getUpdateRevision() != m_compoundShapeRevision)
+	{
+		///clear and update all
+		removeChildAlgorithms();
+		
+		preallocateChildAlgorithms(body0,body1);
+	}
+
+
 	btDbvt* tree = compoundShape->getDynamicAabbTree();
 	//use a dynamic aabb tree to cull potential child-overlaps
 	btCompoundLeafCallback  callback(colObj,otherObj,m_dispatcher,dispatchInfo,resultOut,&m_childCollisionAlgorithms[0],m_sharedManifold);

src/BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.h

@@ -26,6 +26,7 @@ class btDispatcher;
 #include "btCollisionCreateFunc.h"
 #include "LinearMath/btAlignedObjectArray.h"
 class btDispatcher;
+class btCollisionObject;
 
 /// btCompoundCollisionAlgorithm  supports collision between CompoundCollisionShapes and other collision shapes
 class btCompoundCollisionAlgorithm  : public btActivatingCollisionAlgorithm
@@ -36,6 +37,12 @@ class btCompoundCollisionAlgorithm  : public btActivatingCollisionAlgorithm
 	class btPersistentManifold*	m_sharedManifold;
 	bool					m_ownsManifold;
 
+	int	m_compoundShapeRevision;//to keep track of changes, so that childAlgorithm array can be updated
+	
+	void	removeChildAlgorithms();
+	
+	void	preallocateChildAlgorithms(btCollisionObject* body0,btCollisionObject* body1);
+
 public:
 
 	btCompoundCollisionAlgorithm( const btCollisionAlgorithmConstructionInfo& ci,btCollisionObject* body0,btCollisionObject* body1,bool isSwapped);

src/BulletCollision/CollisionShapes/btCompoundShape.cpp

@@ -22,7 +22,8 @@ btCompoundShape::btCompoundShape(bool enableDynamicAabbTree)
 m_localAabbMax(btScalar(-1e30),btScalar(-1e30),btScalar(-1e30)),
 m_collisionMargin(btScalar(0.)),
 m_localScaling(btScalar(1.),btScalar(1.),btScalar(1.)),
-m_dynamicAabbTree(0)
+m_dynamicAabbTree(0),
+m_updateRevision(1)
 {
 	m_shapeType = COMPOUND_SHAPE_PROXYTYPE;
 
@@ -46,6 +47,7 @@ btCompoundShape::~btCompoundShape()
 
 void	btCompoundShape::addChildShape(const btTransform& localTransform,btCollisionShape* shape)
 {
+	m_updateRevision++;
 	//m_childTransforms.push_back(localTransform);
 	//m_childShapes.push_back(shape);
 	btCompoundShapeChild child;
@@ -99,6 +101,7 @@ void	btCompoundShape::updateChildTransform(int childIndex, const btTransform& ne
 
 void btCompoundShape::removeChildShapeByIndex(int childShapeIndex)
 {
+	m_updateRevision++;
 	btAssert(childShapeIndex >=0 && childShapeIndex < m_children.size());
 	if (m_dynamicAabbTree)
 	{
@@ -113,6 +116,7 @@ void btCompoundShape::removeChildShapeByIndex(int childShapeIndex)
 
 void btCompoundShape::removeChildShape(btCollisionShape* shape)
 {
+	m_updateRevision++;
 	// Find the children containing the shape specified, and remove those children.
 	//note: there might be multiple children using the same shape!
 	for(int i = m_children.size()-1; i >= 0 ; i--)
@@ -139,6 +143,7 @@ void btCompoundShape::recalculateLocalAabb()
 {
 	// Recalculate the local aabb
 	// Brute force, it iterates over all the shapes left.
+
 	m_localAabbMin = btVector3(btScalar(1e30),btScalar(1e30),btScalar(1e30));
 	m_localAabbMax = btVector3(btScalar(-1e30),btScalar(-1e30),btScalar(-1e30));
 
@@ -161,9 +166,17 @@ void btCompoundShape::recalculateLocalAabb()
 void btCompoundShape::getAabb(const btTransform& trans,btVector3& aabbMin,btVector3& aabbMax) const
 {
 	btVector3 localHalfExtents = btScalar(0.5)*(m_localAabbMax-m_localAabbMin);
-	localHalfExtents += btVector3(getMargin(),getMargin(),getMargin());
 	btVector3 localCenter = btScalar(0.5)*(m_localAabbMax+m_localAabbMin);
 	
+	//avoid an illegal AABB when there are no children
+	if (!m_children.size())
+	{
+		localHalfExtents.setValue(0,0,0);
+		localCenter.setValue(0,0,0);
+	}
+	localHalfExtents += btVector3(getMargin(),getMargin(),getMargin());
+		
+
 	btMatrix3x3 abs_b = trans.getBasis().absolute();  
 
 	btVector3 center = trans(localCenter);

src/BulletCollision/CollisionShapes/btCompoundShape.h

@@ -59,6 +59,9 @@ ATTRIBUTE_ALIGNED16(class) btCompoundShape	: public btCollisionShape
 
 	btDbvt*							m_dynamicAabbTree;
 
+	///increment m_updateRevision when adding/removing/replacing child shapes, so that some caches can be updated
+	int								m_updateRevision;
+
 public:
 	BT_DECLARE_ALIGNED_ALLOCATOR();
 
@@ -152,6 +155,10 @@ public:
 	///of the collision object by the principal transform.
 	void calculatePrincipalAxisTransform(btScalar* masses, btTransform& principal, btVector3& inertia) const;
 
+	int	getUpdateRevision() const
+	{
+		return m_updateRevision;
+	}
 
 private:
 	btScalar	m_collisionMargin;