Ability to disable collision between specific components

[BoredEngineer]

@kamrann;695342

Yeah I think you’re right that UE4 doesn’t provide this flexibility on the level of individual pairs of bodies. They do something similar for kinematic actors (search ‘MoveIgnoreComponents’ in the engine), but not for simulating bodies it seems.

I’m guessing you’re doing custom physics so not using constraint components/PhysX joints between wheel and chassis? Since in those cases there is a flag available to disable collision between the two bodies constrained by the joint.

Just occurs to me that you could still try a horrible hack - set up a constraint between them anyway, check it’s ‘DisableCollision’ flag, and then configure it as a null constraint that doesn’t constrain any degrees of freedom. Not tried myself, don’t know if it would work and it would probably have a minor performance impact if it did, but worth giving a go.

That could work. But this means that you have to setup such constraint potentially between multiple pairs of simulating components as “DisableCollision” effects only two connected.
In situations when simulating components is at least one component away from root. Like Chassis -> Suspension -> Wheel. One would need an extra set of constraints between each wheel and a chassis which role is to just disable collision. Constraints have rather steep performance hit (I don’t know if non limiting one without drives just idling or iterating over calculations) and they won’t help in case of non-simulating bodies.

In regards to non-simulating bodies. I’ve checked my code again and this issue is limited to BPs actually. From c++, sweeps have input array for bodies to ignore. So I could expose ComponentSweepMulti() to BPs and it would be solved.