PyBullet / BulletRobotics:

Implement collisionFilterPlugin, use setCollisionFilterPair to enable or disable collision detection between specific pairs of objects.
Also, expose setCollisionFilterGroupMask as PyBullet API and in urdf using the tag <collision group="1" mask="2"/>.
See examples/pybullet/examples/collisionFilter.py for an example.
PyBullet default: Lower the warmstarting factor, for maximal coordinates rigid bodies for more stable simulation.
Add btCollisionWorld::refreshBroadphaseProxy to easier recreate the broadphase proxy without adding/removing objects to the world.

examples/pybullet/examples/collisionFilter.py

@@ -0,0 +1,17 @@
+import pybullet as p
+import time
+p.connect(p.GUI)
+planeId = p.loadURDF("plane.urdf", useMaximalCoordinates=False)
+cubeId = p.loadURDF("cube_collisionfilter.urdf", [0,0,3], useMaximalCoordinates=False)
+
+collisionFilterGroup = 0
+collisionFilterMask = 0
+p.setCollisionFilterGroupMask(cubeId,-1,collisionFilterGroup,collisionFilterMask)
+
+enableCollision = 1
+p.setCollisionFilterPair(planeId, cubeId,-1,-1,enableCollision )
+
+p.setRealTimeSimulation(1)
+p.setGravity(0,0,-10)
+while (p.isConnected()):
+	time.sleep(1)