Simulated Parent with Collidable Children?

Hi there,

How would I achieve having a simulated object whose parts are determined dynamically from other child actors? For example, imagine a sandwich. I don’t want all the ingredients to be attached to the bottom bread as a parent - I want all the pieces of the sandwich to be equal, attached to one parent object that is physically simulated, but has no collision of its own.

In Unity, you can have a Rigidbody parent, with all its collision determined by the Colliders in its hierarchy. But in Unreal, it seems I can only physically simulate (and even add forces to) something that has its own geometry already.

I’ve tried hacks, like making the parent very very tiny and invisible, but that is not ideal. I have also considered making one of the children act as the parent, but that is also not ideal. Is there any nice way in Unreal to handle this?

Thank you,
Zi

I want all the pieces of the sandwich to be equal, attached to one parent object that is physically simulated, but has no collision of its own.

How about this sandwich:

  • none of the spheres are simulating physics
  • the cube at the root does simulate it, and the spheres are welded
  • the cube has no collision (it does but we ignore it)

How close am I?

I’ve tried hacks, like making the parent very very tiny and invisible

does not need to be tiny, it’s better when it’s not, actually. Making it invisible is optional.

1 Like

That is awesome, and is the result I want!
It took me a while to get this working dynamically at runtime (instead of pre-authored), but it seems to be working now. Thank you so much!

Having geometry serving as the root object is something I’m very unaccustomed to, coming from Unity. But when in Rome…


Thanks to you, I was able to implement this procedural modular-parts-assembly experiment in a day. Has been very fun and educational. :slight_smile:

1 Like

This doesn’t work with Skeletal Meshes in 5.4

I tried doing this setup with Static Meshes and it worked
But when i tried to do it with Skeletal Meshes it just went through the floor as The Root Static Mesh had no collider and doesn’t take in the Skeletal Mesh Children into account unlike for Static mesh for some reason