Bad deal with curved faces

[Marc Chaumier]

Hi, roy, I send an object, with curved faces that give me problems. It's not the first time that I notice that sort of artefact, and I don't know if it comes from nXt render or autoCAD boule.dwgmodelisation. I've trying a lot of settings on tesselation, in Acad & nXt, with Packet T. or Path T., block or not, sun orientation, I can't get rid of this phenomenon. I've modeled this seat with a sphere and booleans tools. I give the dwg and the jpg, if you have the time to check it...

[Marc Chaumier]

I try to model it with revolution tool, to convert solid to mesh, and smooth and refine.... Nothing works! Only, the artefacts becomes smaller and more numerous, but always remains.

[Marc Chaumier]

Here is a render with autocad engine... not very sexy but no artefacts. It seems that the problem comes from nXt... Am I wrong?

[Roy Hirshkowitz]

It's a tessellation artifact.  You can't completely get rid of it-- you can make it much smaller and less noticeable by increasing the resolution (all of the ways you tried are valid-- don't forget about the parameter in Object Properties too.)