Collision filter doesn't work

[spiritofsim]

I have two boxes that I want to prevent from colliding with each other. I’m setting filter.GroupIndex = -1 for both boxes, but they still keep colliding. Here’s a sample of the code:

`

   func() {
	bodyDef := box2d.MakeB2BodyDef()
	bodyDef.Type = box2d.B2BodyType.B2_dynamicBody
	bodyDef.Position.Set(-3, -3.0)
	body := world.CreateBody(&bodyDef)

	box := box2d.MakeB2PolygonShape()
	box.SetAsBox(1.0, 1.0)
	body.ApplyLinearImpulseToCenter(box2d.B2Vec2{X: 10, Y: -0}, true)

	fixtureDef := box2d.MakeB2FixtureDef()
	fixtureDef.Shape = &box
	fixtureDef.Filter = box2d.MakeB2Filter()
	fixtureDef.Filter.GroupIndex = -1
	f := body.CreateFixtureFromDef(&fixtureDef)
	f.Dump(0)
}()

func() {
	bodyDef := box2d.MakeB2BodyDef()
	bodyDef.Type = box2d.B2BodyType.B2_dynamicBody
	bodyDef.Position.Set(3, -3.0)
	body := world.CreateBody(&bodyDef)

	box := box2d.MakeB2PolygonShape()
	box.SetAsBox(1.0, 1.0)

	fixtureDef := box2d.MakeB2FixtureDef()
	fixtureDef.Shape = &box
	fixtureDef.Filter = box2d.MakeB2Filter()
	fixtureDef.Filter.GroupIndex = -1

	body.CreateFixtureFromDef(&fixtureDef)
}()`