Use a contact listener between bodies who has filter in LibGDX box2D

Question

I am using libGDX with box2D, and I have two bodies who has collision filtering so they cant collide each other.

I am using the groupIndex filter for those bodies, so you can imagine.

But i want to detect the body collision with the contact listener even if they cant collide to each other.

There is a way to do it?.

I did not put any code because this is a question and i thought is not necessary, at least for now...

If you can help me, thank you!.

set their fixtures to sensor libgdx.badlogicgames.com/ci/nightlies/docs/api/com/badlogic/gdx/… — icarumbas
Thanks for your reply, but i cant set it to sensor because i just want to not collide just between that 2 bodies. If i put to sensor the body wont collide with no bodies and i dont want that. As i said i just want to avoid the collision just between these two bodies. Nothing else. — Luis Bermúdez

icarumbas icarumbas · Accepted Answer · 2019-04-18T21:49:46

Use Contact setEnabled method.

In ContactListener:

@Override // In preSolve method. Not beginContact, it matters
public void preSolve(Contact contact, Manifold manifold) {
       short firstBit = contact.getFixtureA().getFilterData().categoryBits;
       short secondBit = contact.getFixtureB().getFilterData().categoryBits;

       if ((firstBit | secondBit) == (BOX_BIT | GROUND_BIT)) {
            System.out.println("Contact " + firstBit + " " + secondBit);
            contact.setEnabled(false);
       }
  }

These bits BOX_BIT and GROUND_BIT are bits of your bodies that shouldn't collide but ContactListener will catch contact between them, set it like:

fixturedef.filter.categoryBits = GROUND_BIT;

Set some other bit for bodies that they should collide.

Hope helps.

Use a contact listener between bodies who has filter in LibGDX box2D

1 Answers