Box volume as child component of physics actor - locking rotation?

Hi all,

As with most things UE4 I imagine there is some easy way to do this but I am going about it in the wrong way.

Basically, I want a physics actor with a box collision slightly larger than the mesh, so it can detect when a fire source is near enough to set fire to the actor. I want to lock the rotation of the box collision so that it follows the physics actor’s position but not rotation, so it is always slightly larger below the actor, to help simulate how heat rises (i.e. it will be easier to set the actor on fire from below).

  • I have a static mesh as my base component for this blueprint - physics are enabled, preset is PhysicsActor.
  • A box collision is set up as a child of the static mesh - physics are disabled, collision preset is Trigger. Physics > constraints > lock rotation x/y/z can be all ticked and it has no effect.

Set up this way, it seems that the box collision locks rotation in the sense that it is locked to match the rotation values of its parent, not that it locks the rotation values when the object is created and will not change regardless of what the parent is doing.

Any ideas/advice is appreciated, I expect I am just approaching this in the wrong way.

Edit: Thought I had found my solution by unticking the auto-weld option on the box collision, but this didn’t make a difference.