Improve damping formula in btRigidBody::applyDamping

Thanks to sparkprime, see http://code.google.com/p/bullet/issues/detail?id=74
Fixed btCompoundShape/btCapsuleShape/btGImpactShape for missing m_shapeType, and added an assert in DemoApplication::localCreateRigidBody for invalid shape types.

Demos/OpenGL/DemoApplication.cpp

@@ -773,6 +773,8 @@ void	DemoApplication::mouseMotionFunc(int x,int y)
 
 btRigidBody*	DemoApplication::localCreateRigidBody(float mass, const btTransform& startTransform,btCollisionShape* shape)
 {
+	btAssert(shape->getShapeType() != INVALID_SHAPE_PROXYTYPE);
+
 	//rigidbody is dynamic if and only if mass is non zero, otherwise static
 	bool isDynamic = (mass != 0.f);
 

Extras/GIMPACT/include/GIMPACT/Bullet/btGImpactShape.h

@@ -105,6 +105,7 @@ protected:
 public:
 	btGImpactShapeInterface()
 	{
+		m_shapeType = GIMPACT_SHAPE_PROXYTYPE;
 		m_localAABB.invalidate();
 		m_needs_update = true;
 		localScaling.setValue(1.f,1.f,1.f);
@@ -150,10 +151,7 @@ public:
 	}
 
 
-    virtual int	getShapeType() const
-    {
-        return GIMPACT_SHAPE_PROXYTYPE;
-    }
+    
 
     /*!
 	\post You must call updateBound() for update the box set.

src/BulletCollision/CollisionShapes/btCapsuleShape.cpp

@@ -21,6 +21,7 @@ subject to the following restrictions:
 
 btCapsuleShape::btCapsuleShape(btScalar radius, btScalar height) : btConvexInternalShape ()
 {
+	m_shapeType = CAPSULE_SHAPE_PROXYTYPE;
 	m_upAxis = 1;
 	m_implicitShapeDimensions.setValue(radius,0.5f*height,radius);
 }

src/BulletCollision/CollisionShapes/btCompoundShape.cpp

@@ -24,6 +24,7 @@ m_collisionMargin(btScalar(0.)),
 m_localScaling(btScalar(1.),btScalar(1.),btScalar(1.)),
 m_dynamicAabbTree(0)
 {
+	m_shapeType = COMPOUND_SHAPE_PROXYTYPE;
 	void* mem = btAlignedAlloc(sizeof(btDbvt),16);
 	m_dynamicAabbTree = new(mem) btDbvt();
 	btAssert(mem==m_dynamicAabbTree);

src/BulletDynamics/Dynamics/btRigidBody.cpp

@@ -143,8 +143,17 @@ void btRigidBody::setDamping(btScalar lin_damping, btScalar ang_damping)
 ///applyDamping damps the velocity, using the given m_linearDamping and m_angularDamping
 void			btRigidBody::applyDamping(btScalar timeStep)
 {
+	//On new damping: see discussion/issue report here: http://code.google.com/p/bullet/issues/detail?id=74
+	//todo: do some performance comparisons (but other parts of the engine are probably bottleneck anyway
+
+//#define USE_OLD_DAMPING_METHOD 1
+#ifdef USE_OLD_DAMPING_METHOD
 	m_linearVelocity *= GEN_clamped((btScalar(1.) - timeStep * m_linearDamping), (btScalar)btScalar(0.0), (btScalar)btScalar(1.0));
 	m_angularVelocity *= GEN_clamped((btScalar(1.) - timeStep * m_angularDamping), (btScalar)btScalar(0.0), (btScalar)btScalar(1.0));
+#else
+	m_linearVelocity *= btPow(btScalar(1)-m_linearDamping, timeStep);
+	m_angularVelocity *= btPow(btScalar(1)-m_angularDamping, timeStep);
+#endif
 
 	if (m_additionalDamping)
 	{