Added a gCompoundChildShapePairCallback to filter (enable/disable) child shape collisions for a btCompoundShape.

Thanks to Rich McDaniel for the patch.
See MyCompoundChildShapeCallback in Demos/ConvexDecompositionDemo/ConvexDecompositionDemo.cpp for usage.

Demos/ConvexDecompositionDemo/ConvexDecompositionDemo.cpp

@@ -46,9 +46,12 @@ GLDebugDrawer	gDebugDrawer;
 #include "../../Extras/BulletMultiThreaded/SpuNarrowPhaseCollisionTask/SpuGatheringCollisionTask.h"
 #endif//USE_PARALLEL_DISPATCHER
 
+#include "BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.h"//for the callback
 
-
+bool MyCompoundChildShapeCallback(const btCollisionShape* pShape0, const btCollisionShape* pShape1)
-
+{
+	return true;
+}
 
 #include "GLDebugFont.h"
 #include <stdio.h> //printf debugging
@@ -80,6 +83,7 @@ void ConvexDecompositionDemo::initPhysics()
 
 
 
+
 ///MyContactCallback is just an example to show how to get access to the child shape that collided
 bool MyContactCallback (
     btManifoldPoint& cp,
@@ -113,6 +117,7 @@ void ConvexDecompositionDemo::setupEmptyDynamicsWorld()
 {
 m_collisionConfiguration = new btDefaultCollisionConfiguration();
 
+
 #ifdef USE_PARALLEL_DISPATCHER
 #ifdef USE_WIN32_THREADING
 
@@ -135,6 +140,7 @@ m_collisionConfiguration = new btDefaultCollisionConfiguration();
 	m_dispatcher = new	btCollisionDispatcher(m_collisionConfiguration);
 #endif//USE_PARALLEL_DISPATCHER
 
+	gCompoundChildShapePairCallback = MyCompoundChildShapeCallback;
 
 	convexDecompositionObjectOffset.setValue(10,0,0);
 
@@ -156,8 +162,6 @@ m_collisionConfiguration = new btDefaultCollisionConfiguration();
 void ConvexDecompositionDemo::initPhysics(const char* filename)
 {
 
-	sEnableSAT = !sEnableSAT;
-
 	gContactAddedCallback = &MyContactCallback;
 
 	setupEmptyDynamicsWorld();
@@ -754,3 +758,22 @@ void	ConvexDecompositionDemo::clientResetScene()
 	exitPhysics();
 	initPhysics("file.obj");
 }
+
+void ConvexDecompositionDemo::keyboardCallback(unsigned char key, int x, int y)
+{
+	if (key=='S')
+	{
+		sEnableSAT= !sEnableSAT;
+		if (sEnableSAT)
+		{
+			printf("SAT enabled after the next restart of the demo\n");
+		} else
+		{	
+			printf("SAT disabled after the next restart of the demo\n");
+		}
+	} else
+	{
+		PlatformDemoApplication::keyboardCallback(key,x,y);
+	}
+
+}

Demos/ConvexDecompositionDemo/ConvexDecompositionDemo.h

@@ -75,6 +75,8 @@ public:
 
 	virtual void displayCallback();
 
+	virtual void keyboardCallback(unsigned char key, int x, int y);
+
 	static DemoApplication* Create()
 	{
 		ConvexDecompositionDemo* demo = new ConvexDecompositionDemo();

src/BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.cpp

@@ -11,6 +11,9 @@ subject to the following restrictions:
 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
 3. This notice may not be removed or altered from any source distribution.
+
+VERSION alterations
+2013-Mar-21: Rich McDaniel - Added callback function to eliminate collisions based on shape testing
 */
 
 #include "BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.h"
@@ -22,6 +25,8 @@ subject to the following restrictions:
 #include "btManifoldResult.h"
 #include "BulletCollision/CollisionDispatch/btCollisionObjectWrapper.h"
 
+btShapePairCallback gCompoundChildShapePairCallback = 0;
+
 btCompoundCollisionAlgorithm::btCompoundCollisionAlgorithm( const btCollisionAlgorithmConstructionInfo& ci,const btCollisionObjectWrapper* body0Wrap,const btCollisionObjectWrapper* body1Wrap,bool isSwapped)
 :btActivatingCollisionAlgorithm(ci,body0Wrap,body1Wrap),
 m_isSwapped(isSwapped),
@@ -129,6 +134,12 @@ public:
 		childShape->getAabb(newChildWorldTrans,aabbMin0,aabbMax0);
 		m_otherObjWrap->getCollisionShape()->getAabb(m_otherObjWrap->getWorldTransform(),aabbMin1,aabbMax1);
 
+		if (gCompoundChildShapePairCallback)
+		{
+			if (!gCompoundChildShapePairCallback(m_otherObjWrap->getCollisionShape(), childShape))
+				return;
+		}
+
 		if (TestAabbAgainstAabb2(aabbMin0,aabbMax0,aabbMin1,aabbMax1))
 		{
 

src/BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.h

@@ -11,6 +11,10 @@ subject to the following restrictions:
 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
 3. This notice may not be removed or altered from any source distribution.
+
+VERSION alterations
+2013-Mar-21: Rich McDaniel - Added accessor to child algorithms in btCompoundCollisionAlgorithm
+2013-Mar-21: Rich McDaniel - Added callback function to eliminate collisions based on shape testing
 */
 
 #ifndef BT_COMPOUND_COLLISION_ALGORITHM_H
@@ -28,6 +32,11 @@ class btDispatcher;
 class btDispatcher;
 class btCollisionObject;
 
+/* 2013-Mar-21 - Rich McDaniel */
+class btCollisionShape;
+typedef bool (*btShapePairCallback)(const btCollisionShape* pShape0, const btCollisionShape* pShape1);
+extern btShapePairCallback gCompoundChildShapePairCallback;
+
 /// btCompoundCollisionAlgorithm  supports collision between CompoundCollisionShapes and other collision shapes
 class btCompoundCollisionAlgorithm  : public btActivatingCollisionAlgorithm
 {
@@ -37,6 +46,7 @@ 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();
@@ -49,6 +59,12 @@ public:
 
 	virtual ~btCompoundCollisionAlgorithm();
 
+	btCollisionAlgorithm* getChildAlgorithm (int n) const
+	{
+		return m_childCollisionAlgorithms[n];
+	}
+
+
 	virtual void processCollision (const btCollisionObjectWrapper* body0Wrap,const btCollisionObjectWrapper* body1Wrap,const btDispatcherInfo& dispatchInfo,btManifoldResult* resultOut);
 
 	btScalar	calculateTimeOfImpact(btCollisionObject* body0,btCollisionObject* body1,const btDispatcherInfo& dispatchInfo,btManifoldResult* resultOut);
@@ -63,6 +79,7 @@ public:
 		}
 	}
 
+	
 	struct CreateFunc :public 	btCollisionAlgorithmCreateFunc
 	{
 		virtual	btCollisionAlgorithm* CreateCollisionAlgorithm(btCollisionAlgorithmConstructionInfo& ci, const btCollisionObjectWrapper* body0Wrap,const btCollisionObjectWrapper* body1Wrap)