In the mesh editor, under Details > Collision > Complex Collision Mesh, I selected a mesh made to be the collision mesh of another mesh. It shows up properly in the mesh editor viewport.
I tried changing the Collision Complexity setting, none of the options help. ‘Use Complex Collision as Simple’ seemed promising, but it just sets up a duplicate of the mesh the collision shape is for, instead of using the custom shape that I set up to replace that.
If you already assigned custom collision mesh, I think by turning on ‘use complex collision as simple’ would tell the engine to use that as collision (I could be totally wrong here). But what you could always do is to put both your render mesh & collision mesh in your scene, but turn visibility for the collision mesh off (while the collision mesh is set to use complex & render mesh set to no collision).
That work around makes total sense… I suppose it would be the same as far as performance.
Now that this opens my mind, I’ll optimize by using only a few such shapes to cover the larger area.
Btw, no, ‘use complex collision as simple’ only causes the normal behaviour of using the render mesh to create the collision mesh.
Thanks for your help. I marked it as the solution, though it leaves open the mystery of how to use the function I was trying to use. It’s better this way.