Occlusion Culling with Backfaces imported from sketchup

Occlusion Culling not working as expected for FBX imported from Sketchup

I have a scene with 1.9M tris that is imported from sketchup as fbx. I have to export two-sided faces, or else a bunch of objects are missing (drawn the wrong way, even though in sketchup the back faces look correct)

When I import that model, and bake occlusion culling with values of 1, 0.1 and 100 for occluder, hole and backface threshold, I get very odd behaviour when I play the scene.

Objects which I expect to not be occluded (ex a table in plain sight) jump in and out as the camera is moved. Most objects, but not all are behaving this way.

I also noticed that the visibility lines are very short - they don't hit the back walls as I expect them too. there seems to be an arbitrary distance that the culler goes to.

I've tried different values for backface threshold, from 5 to 100, but none seem to give me good results. Default settings also gave me the same results.

All objects are static occlude and occlude for simplicity

What settings can I use to get this sketchup model working correctly.

I'm on 5.5.1p2, Bug report https://fogbugz.unity3d.com/default.asp?910227_g3b4b2haf9gko69e

 

Update - the issue happens when I change a material from transparent to opaque.

 

Sketchup usually has a lot of problems with normals. It sounds like your issues are with the model, not unity. Bring the model into blender or maya or something like that and clean it up, that will most likely solve your issues.

 

I ended up just deleting the material, creating a new opaque one , and applying it to the transparent objects