Unexplainable Render Outcome

[hamay]

Good day,

I am trying to render a metal object and have attached the relevant wireframe as well as the outcome. Could someone please advise how to get rid of the line on the surface?

—Hamay

Additional information:

• I am using KS 7.2109 Pro on a Mac
• I am using the standard metal material
• I don't have round edges activated
• My lighting setup is default set, only HDRI, no physical lights
• This issue disappears if I enter performance mode — however shows in rendering again
• I have re-tessellated my model at the highest setting possible.
• I have recalculated normals within KS
• I have exported from Rhino as .obj, .igs, .stp and imported to KS

[Greg_R]

Hamay,

Need some more info on your post, what software are you using to create model?  Can you share the model?  Are you using a plugin?

[hamay]

Greg,

Appreciate your answer. I am using Rhino for modeling, export as .obj and import that file to KS using File > Import.

I have attached the object in question and hope we can solve that issue.

—Hamay

[Greg_R]

I believe you need to adjust your mesh settings when exporting from Rhino as an obj.  There is a slider that pops up and you need more polygons.  If you are exporting as an iges or stp, you shouldn't have that problem unless your tessellation setting in KS is set very low, or if the object is already a mesh in rhino.

Also I would look at using the Keyshot plugin for Rhino.  Its been a while since I've used it regularly, but I remember it being pretty good.

[hamay]

That's the export settings in Rhino and the import settings in KS for the .iges file. The outcome is the same.

Were you able to get a good result with a higher mesh setting?

[Greg_R]

When you are importing an iges in to KS, you want the tessellation value to be much lower.  I usually import files at .3 to .4

The rhino settings in your screenshot are only for the viewport, I don't think that they affect the exported files in any way.

Also, keyshot will open up the .3dm file from rhino directly.

[hamay]

Thanks, I'll try that.

Are you getting the same result with the source file I have included?

[TGS808]

That "line" you are seeing on the surface is the other side of the inner ring reflecting back on itself.   I added a red sphere as a reference point. You can see the sphere reflected on the other side is perfectly aligned with the "line".  If you add a bit of roughness to the metal material the line beings to smooth out (but the metal looks less reflective). Add total roughness and the line is gone because there are no reflections anymore. (see examples)  The reason you don't see it in performance mode is because in performance mode, the reflections are turned off.

[Greg_R]

Hamay,

The file you uploaded was an obj, which is already a mesh and there is nothing you can do in KS to improve the mesh quality of an existing mesh.  I got the same result you are.

Can you share the rhino(3dm) file?  If lowering the tessellation value when importing into KS isn't giving you the desired result, I suspect your geometry in rhino may already be a mesh and this is whats causing the confusion.

[hamay]

TGS808,

Thanks, now I feel relieved and dumb at the same time 

It makes perfect sense after reading it and it didn't even occur to me that this could be a self shadow after I did that test with different materials.

—Hamay