(Unreal version 5.0.2-20280985+++UE5+Release-5.0)
I’m creating a bunch of actors that use Nanite mesh. The meshes have 3 material groups, none of which use WPO, and it’s just a normal static mesh rigid body. The one that can’t be clicked is a literal box shape, essentially a steamer trunk-shaped crate. A bunch of other meshes created using an identical process (just different shapes that tend to be more rounded and less square) are clickable fine, they’re also all Nanite, and they all use identical parent materials, only difference is unclickable ones happen to use the green material instance.
If I disable Nanite on the meshes, they’re clickable again instantly. If I disable and then re-enable Nanite, they often start working again, but when clicked, the selection outline is odd. Instead of surrounding the entire object, only one mesh group is surrounded. As it happens, each side of the box has a green-colored center part and metallic framed edges, and it chooses to draw the highlight outline around only the green parts.
I have a suspicion that when they stop working, it’s because the engine has arbitrarily chosen to make a different material group clickable. Because when in not-clickable state, sometimes if I click in just the right place, they selected? But they don’t appear to be visually selected. Maybe I’m just clicking on the metallic edge in that case or the little front medallion, which are small and I likely wouldn’t see the outline.
When the clicks fall through, what gets selected instead is something called “Brush (Instance)”. Which doesn’t exist in my scene, as far as I can tell. If it helps, it reports the position of that Brush Instance as (-2835, -2075, 195).
As an added oddity, all of these meshes (even the ones that select normally) have what I can only describe as wiggly outlines when selected. If I make them non-Nanite and select them, I get the normal orange outline, totally standard. If I turn on Nanite and select them, the orange outline is, for lack of a better term, wiggly. Like that effect you get in hand-drawn animation where the line changes a tiny bit each frame because of how pencil lines work. It’s quite bizarre.
I’m assuming all of this is down to Nanite objects not having complex collision. As confirmed by going into the mesh editor and attempting to turn on complex collisions and seeing absolutely nothing on these Nanite meshes, but it of course draws fine on them if I turn Nanite off. Nanite meshes are, I gather, supposed to use some kind of Nanite proxy for complex collisions, and presumably these objects aren’t making it in there. Which would imply that this could actually cause gameplay problems too? Guessing that any complex traces would similarly fail to hit them? They behave normally as rigid bodies, but that would be because they still have functioning simple collisions- a single essentially-a-box convex collider, if that matters.
EDIT: Correction, the click behavior is even weirder. Depending on which material group I click, I get completely random things. As it happens, right now when I click the green sides of these boxes, it selects an entirely different (also Nanite) mesh in the scene. Though it draws as though I’ve selected that box, and outlines only the green sides of the box. Meanwhile if I click the metallic edges of the box, NOW it selects the actual box these relate to, and only draws an outline around the metallic edges. Quite bizarre. Presumably the bug is down to Nanite meshes with multiple material groups? Not sure why the others all work fine though.
