Adding collision to models imported from Sketchup

I’ve been using Sketchup recently to make all my models for games as Blender is too complicated and I still haven’t even installed or learned how to use Maya yet. I’ve been trying to import a model from Sketchup but it has no collision once in the editor. The model is an open topped ring with a risen circular platform in the center of the floor.

I’ve used all solutions that i’ve been told and none have been able to add proper collision. I’ve tried turning “Generate Collisions” on in the import settings. I’ve tried using the sketchyphysics plugin for Sketchup, i’ve tried exporting as .fbx (which is actually better than .dae), i’ve even tried to turn every section of the model into a different group so each section has its own mesh and still the bullets i’m trying to fire at it won’t collide with it.

So far, after a long time of playing with it, i’ve managed to make some bullets reflect off the wall after colliding with certain places, although i have them set to destroy themselves once they hit a wall, which is quite wierd. The bullets themselves do have collision, as i have a block on the scene that actually moves once a bullet hits it, but the bullets clip right through the arena wall and i have no clue about where they coliide and where they don’t. Basically, the walls of the ring have a small red indent running the whole way around so i can add some red lights in there, but the bullets seem to hit the red indent, bounce off, then hit the actual wall, bounce off that, but then clip right through the red indent when they hit it again…

It’s like it collides when it wants to. Also, i’ve been getting a ton of errors saying “Compute mass inertia tensor failed for one of the actor’s mesh shapes. Please change mesh geometry or supply a tensor manually”, which i don’t understand at all.

The error you get comes from the fact that some parts of your model are just planes and a plane is just a geometric entity, totally flat. The collider (in 3D) needs be a volume. So when generating the automatic collider based on mesh, some parts are not volume and collision may not be detected.

I think you would be better creating the collision box manually, at least where you do not need extra precision. Just add some box colliders and make them match the mesh. It won’t be as precise but you probably do not need it. On top of that, it is way faster to use boxes than any mesh collider.