couche de collision un masque de collision godot
Collision mask bit is for choosing what layer should be collided.
Let's assume we set collision layer and mask layer as below.
Player node : collision layer is on 1st bit / mask layer is on 2nd,3rd bit
Enemy node : collision layer is on 2nd bit / mask layer is on 1st bit
Object node : collision layer is on 3rd bit / mask layer is on 1st bit
then,
Player mask(2) == Enemy layer(2)
Player mask(3) == Object layer(3)
so, Player can be collided with Enemy and Object.
but Enemy nodes are not collided each other or Object nodes.
Because Enemy mask(1) != Enemy layer(2) / Enemy mask(1) != Object layer(3)