Bump mapping a mesh from a CAD model

[berglte]

I'm having a problem applying noise as a bump map to a dense mesh originating from a cad model.

I've imported the already triangulated mesh in as .obj and it has normals generated for each point.

It renders just fine in pbr with a simple diffuse+specular custom shader except when I apply a turbulent noise via the displace along normals VOP node. I've connected its N output to both diffuse and specular bsdf nodes N input.

This results in some smaller, long triangles becoming darker than the surrounding mesh and causing visible artifacts in the render.

Any suggestions on how to fix this? All help is very much appreciated.

[kleer001]

I'm having a hard time visualizing your problem. Please post an example image.

[Marc]

Could it be displacement bound artifacts? Try increasing the displace bounds and see if your problems resolve themselves.

 

[berglte]

I tried adding the vm_displacebound property to the shader with different values but that had no effect. Thanks for the suggestion anyway Marc!

bump_example.jpg shows the correct bump behavior rendered in Octane, the artifacts that appear with Mantra and the mesh wireframe which relates to the artifacts. Maybe there's something weird with the mesh that only shows up when I apply the bump mapping? A lot of the polygon primitives are detached and there are overlapping points as a result, but the point normals should be fine.

I also attached a screenshot of my shader network, maybe there's something that I've setup in a wrong way?

[f1480187]

I don't know any good rendering setting to eliminate this artifacts with long triangles, but as alternative solution, which I usually do, try to remesh your geometry. You may try converting to VDB and back to polygons, Divide SOP in bricker mode, Remesh SOP or combination of this tools. Houdini does not support STEP format, and you probably won't get adequate results with IGES, but it is also an option. Most robust solution is probably export again with another meshing settings, if they are present. For example, Rhino's mesher able to generate good watertight isotropic geometry with UVs and normals.

eliminate_long_thin_triangles.zip

[berglte]

Thanks for the example file!

Looks like I might need to just re-export the geometry this time to get around the problem. The problem disappears eventually when I crank up the settings in the exporter, but also means I get a really dense mesh to work with that's not optimal.

A rendertime solution would still be great for future projects though.