Function B2ContactUpdate

DynamicsB2Contact.go:449–525

Update the contact manifold and touching status. Note: do not assume the fixture AABBs are overlapping or are valid.

(contact B2ContactInterface, listener B2ContactListenerInterface)

// Update the contact manifold and touching status.
// Note: do not assume the fixture AABBs are overlapping or are valid.
func B2ContactUpdate(contact B2ContactInterface, listener B2ContactListenerInterface) {
	oldManifold := *contact.GetManifold()

	// Re-enable this contact.
	contact.SetFlags(contact.GetFlags() | B2Contact_Flag.E_enabledFlag)

	touching := false
	wasTouching := (contact.GetFlags() & B2Contact_Flag.E_touchingFlag) == B2Contact_Flag.E_touchingFlag

	sensorA := contact.GetFixtureA().IsSensor()
	sensorB := contact.GetFixtureB().IsSensor()
	sensor := sensorA || sensorB

	bodyA := contact.GetFixtureA().GetBody()
	bodyB := contact.GetFixtureB().GetBody()
	xfA := bodyA.GetTransform()
	xfB := bodyB.GetTransform()

	// Is this contact a sensor?
	if sensor {
		shapeA := contact.GetFixtureA().GetShape()
		shapeB := contact.GetFixtureB().GetShape()
		touching = B2TestOverlapShapes(shapeA, contact.GetChildIndexA(), shapeB, contact.GetChildIndexB(), xfA, xfB)

		// Sensors don't generate manifolds.
		contact.GetManifold().PointCount = 0
	} else {
		// *B2Contact is extended by specialized contact structs and mentionned by B2ContactInterface but not implemented on specialized structs
		// Thus when
		//spew.Dump("AVANT", contact.GetManifold())
		contact.Evaluate(contact.GetManifold(), xfA, xfB) // should be evaluated on specialisations of contact (like CircleContact)
		//spew.Dump("APRES", contact.GetManifold())
		touching = contact.GetManifold().PointCount > 0

		// Match old contact ids to new contact ids and copy the
		// stored impulses to warm start the solver.
		for i := 0; i < contact.GetManifold().PointCount; i++ {
			mp2 := &contact.GetManifold().Points[i]
			mp2.NormalImpulse = 0.0
			mp2.TangentImpulse = 0.0
			id2 := mp2.Id

			for j := 0; j < oldManifold.PointCount; j++ {
				mp1 := &oldManifold.Points[j]

				if mp1.Id.Key() == id2.Key() {
					mp2.NormalImpulse = mp1.NormalImpulse
					mp2.TangentImpulse = mp1.TangentImpulse
					break
				}
			}
		}

		if touching != wasTouching {
			bodyA.SetAwake(true)
			bodyB.SetAwake(true)
		}
	}