Hello again, sorry many questions today
I have imported an STL file from a CAD app. Well, you know how messy it is modelling wise.
However in my experience with other apps it is possible to get normal renders with these kind of objects.
In Houdini I can't get a good render. I tried the node facet, normal, etc, but could not fix the problem. I think the “Polydoctor” node could come in handy, however I didn't manage to use it properly. Any ideas about which options I should set?
What's strange is that some materials increase the problem. Check the attachment. With the material “piano lacquer” I have almost a normal result, but with the “titanium” material, all hell breaks loose.
Any suggestion would be appreciated. Thanks
Gz

I would revisit the Normal node. Place it at the very end of the chain and move your Display/Render flag so the Blue/Pink circle surrounds it. Then try rendering with the normal applied. Try the various data contexts available on the node (i.e. point, vertex and primitive).

Set the normal weighting to ‘from face area’ would a good start, but ideally you would get good normals to begin with from the host application that exported the model.

apart from normals I'd check if you have any Anisotropy on your Titanium material, as it surely looks like what anisotropy would do without proper tangent vectors, which are by default computed from UVs (so without correct continuous UV attribute on your geo you'd get different anisotropy directions per face)

Thanks VERY MUCH guys!! Here's how I fixed it:

- For the black parts needing piano lacquer : I put a normal node at the bottom, just before the “OUT” null, with these settings:
Group Type = guess from group
Add normals to = points or vertices
Cusp angle = 60 but it doesn't seem to have an effect
Weighting method = by face area

- For the metallic parts needing Titanium: anisotropy and anisotropy direction at 0.

- I would add that I have a Facet node at the top of the network (just below the “object merge” node) with “cuspt polygons” checked and its angle is 30.


Thanks again you rock