Incorrect collision result when using DynamicAABBTreeCollisionManager

[lwygzh]

Hi,

I was trying to use the Collision Manager to compute the collision between two objects (as a toy example)

sphere = fcl.Sphere(0.1)
sphere_obj = fcl.CollisionObject(sphere)
M_sphere = fcl.Transform3f.Identity()

box = fcl.Box(6.0, 4.0, 1.0)
box_obj = fcl.CollisionObject(box)
M_box = fcl.Transform3f.Identity()
M_box.setTranslation(np.array([0.0, 1.0, 0.0]))
box_obj.setTransform(M_box)

collision_manager = fcl.DynamicAABBTreeCollisionManager()
collision_manager.registerObject(box_obj)
collision_manager.setup()

# first scenario
callback = fcl.CollisionCallBackDefault()
M_sphere.setTranslation(np.array([1, 2, 0.0]))
sphere_obj.setTransform(M_sphere)
collision_manager.collide(sphere_obj, callback)
is_collision = callback.data.result.isCollision()
print("Is collision: ", is_collision)

# second scenario
callback.data.result.clear()
M_sphere.setTranslation(np.array([4, 2, 0.0]))
sphere_obj.setTransform(M_sphere)
collision_manager.collide(sphere_obj, callback)
is_collision = callback.data.result.isCollision()
print("Is collision: ", is_collision)

# third scenario
callback.data.result.clear()
M_sphere.setTranslation(np.array([1, 2, 0.0]))
sphere_obj.setTransform(M_sphere)
collision_manager.collide(sphere_obj, callback)
is_collision = callback.data.result.isCollision()
print("Is collision: ", is_collision)

However, I get the collision results as "True, False, False". Since the third scenario is the same as the first scenario the output should be "True, False, True". Can someone help me understand what is wrong in the code?

When I create a new callback = fcl.CollisionCallBackDefault() for each scenario the result is then correct. So I suspect there is some issues with how the callback result is updated.

Thanks!

[lmontaut]

Hi @lwygzh,
Thank you for checking out hppfcl!
The broadphase collision callback has a boolean field, done which tells whether or not the process of collision detection should continue or not.
When resetting the callback, you should therefore do:

callback.data.result.clear()
callback.data.done = False

I will do a PR on the devel branch to have a callback.data.clear() method which handles both clearing the collision result and the boolean.

Best,
Louis

Edit: This is the PR: #509
With it, you won't have to call clear for the callback's data as it will be automatically cleared by the broadphase manager when calling manager.collide(callback).