subdivision smoothing issues/faceting

[johnjoe]

Hello,

I am having an issue with smoothing in Vray for Maya, both using 'convert to mesh preview' and also with the extra vray attribute 'subdivide at rendertime'.

When heavily subdividing the mesh on an object i am getting some areas which do not smooth correctly, even when subdividing to a very high level of detail. (see image below) The rest of the mesh aside from that displayed here smooths correctly.



To try and combat this, i used a low resolution version of the model and applied the extra Vray attribute 'render as subdivision surface'.
This fixed the issue of smoothing in the area where i was having issue before but created more artefacts elsewhere, specifically along the cut lines of the low poly mesh.



To try and combat the issue another way, I applied the Vray extra attribute 'render as subdivision surface' to the heavily subdivided mesh. All this did was increase the amount and density of the artefacts (along cut lines).
I have checked that all the faces on the mesh have softened normals, and also checked for lamina/ co-planar faces. I also tried increasing the 'secondary ray bias' to 0.010 to try and combat the issue. sadly, none of these things have fixed the issue. (see image below)



Any ideas on how I can get around the issue would be greatly appreciated.

Thanks in advance,

Joe.

[vlado]

It seems to me there are problems with the mesh itself; if you wish, you can send it to vraymaya@chaosgroup.com and we'll debug it, but it might also be useful to check the mesh at this particular place any errors, like double vertices/faces/edges.

Best regards,
Vlado

[johnjoe]

Thanks for the prompt reply Vlado.

I am going to make some further investigations this afternoon, if I don't manage to fix the issue then I'll send over a file for you to look at.

Thanks again.

Joe

[RobPhoboS]

Hi Joe,

Do you have anything plugged into the Reflection colour ?
I had a problem with some materials that had ramps in them, they were just some free ones I downloaded from the net. They caused problems in the reflection channel only (add some render elements to check where the problem is).
(I swapped out for the vray fresnel instead)

Obviously, it may not be that at all, but worth mentioning.

[johnjoe]

Thanks for the reply RobPhoboS; after further investigation I discovered that the problem was in the images I was using on the Vraylight dome when rendering, they had seams in them and the artefacts stopped appearing when I tried another HDRI probe (for example, Paul Debevec's Uffizi probe).

Thanks again for the help guys.

Joe