I copied the “FirstPersonProjectile.uasset” from the FPS sample into my project and rebuild it into my new BaseProjectile. I still have absolutely no idea why that one works and mine doesn’t since I can’t find any difference between the two blueprints aside from having a SceneRoot component (which I can’t even delete).
I would still like to know though what I and all those other people did wrong. Because not one of these posts I could find anywhere on Google had an actual answer other than some silly workaround. Meaning nobody knows?
Secondly: Why does unchecking “simulate physics” also prevent collision-checks including overlaps? Intended?
I found the problem! Might be a UE4 bug. Apparently the moment I ctrl+x the SphereComponent from the FirstPersonProjectile and paste it back (this creates a scene-root so the sphere collision component is no longer the root) breaks it entirely. Only applies to actors that have the “simulate physics everywhere unchecked”. So the CollisionComponent MUST BE THE ROOT in the actor-blueprint and when not, ALL COLLISION (except collisions with pawns for some reason) is gonna be ignored by the game for this object. I reproduced it across several projects. If Scene_Root is the root (which is default) it will break.
Sadly you can’t override the Scene_Root in a child-component… Man this whole thing is so weird I dunno why they implemented the Editor to work this way. So you gotta put in a dummy-component instead of the default-root, then replace it in the child in the constructor with the real thing. Only then can you replace it…
Note that adding additional collision-components does NOT work (only the root-collision-component works).
Because of this insanely weird behavior my guess is that this is a bug.