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javalibgdxbox2d

Libgdx contact fixture

I'm trying to implement Box2d's ContactListener interface. The method called when a contact happens receives a Contact object. This object then provides getFixtureA and getFixtureB getters.

Is there a rule, that says which fixture is assigned to A and which to B or do I have to check all combinations, as in:

I have bodies X, Y, Z and want to check if X and Y collided. Do I have to always check if (A == X && B == Y) || (A == Y && B == X) or is one of the two sufficient?

(A is contact.getFixtureA(); and B is contact.getFixtureB();)

Solution

  • You would have to check both possibilities, Box2D provides no specific ordering.

    As irresistable force says, there would be no logical ordering for fixtures in a contact:

    If they were ordered somehow, how would they be ordered?