How to set up custom complex collision Mesh?

I have now spent hours trying to figure out how to use a low poly version of a mesh as a complex collision for the high poly mesh.

At first I thought, simply, there is this field where I can put a complex collision mesh, but that doesn’t seem to work. It does show up in the static mesh view, but when I use the “show collision” command in game, it still uses the full complex collision of the high poly mesh.

Then looking for answers I stumbled across that I need to set up the collision with prefixes in Blender and then import it. But that doesn’t seem to be made for what I’m trying to do. I would need to set up several simple shapes in Blender and name them correctly for this to work.
Since I already have the low poly version from pre-modeling, the best solution would be to just use that as the complex collision, but I can’t get that to work.

So how do you use the complex collision mesh field? Just put a mesh there and select complex as simple doesn’t do it.

Set the collision on the high poly to none, and the low poly to ‘complex as simple’. That should do it, no?

I already had the low poly set to complex as simple, but that didn’t work either.
By none do you mean set the collision preset to “NoCollision”? I tried that as I didn’t see another way to disable it, but then I don’t have any collision at all.

When you set the low poly to complex as simple, it uses the actual geo to make the collision. It has to work :slight_smile:

Well it does sort off. It is there in the Mesh view but I can’t get it to use it ingame.

  • If I set the high poly to use complex as simple it uses the geometry of the high poly one
  • If I leave it at project default it uses the simple collision of the high poly mesh
  • If I set the collision preset on the high poly to “NoCollision” it doesn’t have any collision in game


This is how it looks on the high poly one in the Mesh view.


And this is how it looks in game.

The high poly model is split into multiple parts as to mimic construction. This is way there is only complex collision from the high poly in parts of the custom complex collision.
Unless this is the issue because they are to diffrent?


Complet it looks like this with only the first part having collision. Therefore the custom collision on the first part of the whole model.


low poly settings


high poly settings

Yeah, don’t try and configure it in the mesh editor. Just actually put two separate meshes in the game. The highpoly one for the visuals ( with collision turned off ), and the low poly one with ‘complex as simple’ and set to ‘hidden in game’.

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Well I guess that is a solution.

But what is the use of the complex collision Mesh field then?

Well, good question. It may be that it’s supposed to work the way you think. It might be there is another ( correct ) way to use this. Or maybe it’s just broken.

The main thing with UE is not to sweat this kind of thing too much, otherwise you’ll never get there… :slight_smile:

Most people would not try and make this as one mesh, to be fair. And very probably block the thing out with blocking volumes rather than trying to get the building collisions right.

Yeah I normally try to find different solutions but here I just wasn’t thinking about it besides that I now need to change some things in Blueprints to get it to work properly.

That would probably be a better solution but I figured since I already had a low poly model it would be much easier to just set it as complex collision mesh but then it didn’t work and I could also just done it diffrently in that time ^^

Thanks for your help!

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Hello there, and sorry for bumping a year-old topic; but I have the same exact problem, in UE 5.3:

I was modelling a cavern, where the player will be flying around inside of it (like in good old Descent). So I’ve created two meshes for the cavern shell, one for rendering, and one for collision. The rendering mesh was set to use collision mesh as its complex collider like this:

However, inside the editor & in game, I get this:

The above solution, placing the render mesh and collision mesh on top of each other, does work; but it sounds like a bit stop-gap solution for me, especially when it comes to scaling the project scope up, and creating labyrinthine cavern systems, etc. While it is possible to solve this problem with blueprints, I still have to ask: Why the option to set custom complex meshes still doesn’t work as intended? It would help a lot on creating really complex geometry, where setting up UCX hulls wouldn’t be as feasible? I’m curious.

If it does work, but we’re missing something, please let us know!
And thanks in advance…