bugfix: for btCompoundShape::getChildTransform: return (const) reference to btTransform, not a copy.

added btCompoundShape::updateChildTransform
Thanks to ejtttje, see http://bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=2831

src/BulletCollision/CollisionShapes/btCompoundShape.cpp

@@ -17,7 +17,7 @@ subject to the following restrictions:
 #include "btCollisionShape.h"
 #include "BulletCollision/BroadphaseCollision/btDbvt.h"
 
-btCompoundShape::btCompoundShape()
+btCompoundShape::btCompoundShape(bool enableDynamicAabbTree)
 : m_localAabbMin(btScalar(1e30),btScalar(1e30),btScalar(1e30)),
 m_localAabbMax(btScalar(-1e30),btScalar(-1e30),btScalar(-1e30)),
 m_collisionMargin(btScalar(0.)),
@@ -25,10 +25,14 @@ m_localScaling(btScalar(1.),btScalar(1.),btScalar(1.)),
 m_dynamicAabbTree(0)
 {
 	m_shapeType = COMPOUND_SHAPE_PROXYTYPE;
+
+	if (enableDynamicAabbTree)
+	{
 		void* mem = btAlignedAlloc(sizeof(btDbvt),16);
 		m_dynamicAabbTree = new(mem) btDbvt();
 		btAssert(mem==m_dynamicAabbTree);
 	}
+}
 
 
 btCompoundShape::~btCompoundShape()
@@ -76,6 +80,23 @@ void	btCompoundShape::addChildShape(const btTransform& localTransform,btCollisio
 
 }
 
+void	btCompoundShape::updateChildTransform(int childIndex, const btTransform& newChildTransform)
+{
+	m_children[childIndex].m_transform = newChildTransform;
+
+	if (m_dynamicAabbTree)
+	{
+		///update the dynamic aabb tree
+		btVector3 localAabbMin,localAabbMax;
+		m_children[childIndex].m_childShape->getAabb(newChildTransform,localAabbMin,localAabbMax);
+		ATTRIBUTE_ALIGNED16(btDbvtVolume)	bounds=btDbvtVolume::FromMM(localAabbMin,localAabbMax);
+		int index = m_children.size()-1;
+		m_dynamicAabbTree->update(m_children[childIndex].m_node,bounds);
+	}
+
+	recalculateLocalAabb();
+}
+
 void btCompoundShape::removeChildShapeByIndex(int childShapeIndex)
 {
 	btAssert(childShapeIndex >=0 && childShapeIndex < m_children.size());
@@ -88,6 +109,8 @@ void btCompoundShape::removeChildShapeByIndex(int childShapeIndex)
 
 }
 
+
+
 void btCompoundShape::removeChildShape(btCollisionShape* shape)
 {
 	// Find the children containing the shape specified, and remove those children.
@@ -99,6 +122,8 @@ void btCompoundShape::removeChildShape(btCollisionShape* shape)
 			m_children.swap(i,m_children.size()-1);
 			m_children.pop_back();
 			//remove it from the m_dynamicAabbTree too
+			//@todo: this leads to problems due to caching in the btCompoundCollisionAlgorithm
+			//so effectively, removeChildShape is broken at the moment
 			//m_dynamicAabbTree->remove(m_aabbProxies[i]);
 			//m_aabbProxies.swap(i,m_children.size()-1);
 			//m_aabbProxies.pop_back();

src/BulletCollision/CollisionShapes/btCompoundShape.h

@@ -46,23 +46,23 @@ SIMD_FORCE_INLINE bool operator==(const btCompoundShapeChild& c1, const btCompou
 		c1.m_childMargin    == c2.m_childMargin );
 }
 
-/// btCompoundShape allows to store multiple other btCollisionShapes
+/// The btCompoundShape allows to store multiple other btCollisionShapes
 /// This allows for moving concave collision objects. This is more general then the static concave btBvhTriangleMeshShape.
+/// It has an (optional) dynamic aabb tree to accelerate early rejection tests. 
+/// @todo: This aabb tree can also be use to speed up ray tests on btCompoundShape, see http://code.google.com/p/bullet/issues/detail?id=25
+/// Currently, removal of child shapes is only supported when disabling the aabb tree (pass 'false' in the constructor of btCompoundShape)
 ATTRIBUTE_ALIGNED16(class) btCompoundShape	: public btCollisionShape
 {
-	//btAlignedObjectArray<btTransform>		m_childTransforms;
-	//btAlignedObjectArray<btCollisionShape*>	m_childShapes;
 	btAlignedObjectArray<btCompoundShapeChild> m_children;
 	btVector3						m_localAabbMin;
 	btVector3						m_localAabbMax;
 
-	//btOptimizedBvh*					m_aabbTree;
 	btDbvt*							m_dynamicAabbTree;
 
 public:
 	BT_DECLARE_ALIGNED_ALLOCATOR();
 
-	btCompoundShape();
+	btCompoundShape(bool enableDynamicAabbTree = true);
 
 	virtual ~btCompoundShape();
 
@@ -88,15 +88,18 @@ public:
 		return m_children[index].m_childShape;
 	}
 
-	btTransform	getChildTransform(int index)
+	btTransform&	getChildTransform(int index)
 	{
 		return m_children[index].m_transform;
 	}
-	const btTransform	getChildTransform(int index) const
+	const btTransform&	getChildTransform(int index) const
 	{
 		return m_children[index].m_transform;
 	}
 
+	///set a new transform for a child, and update internal data structures (local aabb and dynamic tree)
+	void	updateChildTransform(int childIndex, const btTransform& newChildTransform);
+
 
 	btCompoundShapeChild* getChildList()
 	{