VRayDisplacementMod problem - black gaps

[airion]

Hi guys,

I have some questions about vray displacement.

Today i tried to get an object from max to mudbox, and than make it come back with an exact match in terms of what i see in mudbox - and what i render in max 2013 64bit ( vray 2.40.03 )
I did research on the forum and got a decent result, but still it is not perfect!

I wonder if it is possible since i seem to be getting small black artifacts at the uv edges.
Avoiding them is what is suggested almost on each thread but still, If you cant avoid i would like to know how to minimise them or even how to get rid of them.

I made the cylinder in max, exported it, and added my detail in mudbox.
I recreated my level 2 UV
and than i exported my map ( see the attached screenshot for the settings )
I tried alot of varriations but still i dont get the perfect result!

any help would be appriciated!
tnx
Air

[Morbid Angel]

did you try baking with subdivision and not raycasting? also, on the sharp edges, you might want to check - keep continuity for edges not to tear.

[vlado]

I think you need to turn off "smooth UVs at borders" in the V-Ray displacement modifier - as you see in Mudbox the boundaries of the UV patches are not smoothed.

Best regards,
Vlado

[airion]

Hi guys,

thx for the answers. I tried both and no succes.

@ Vlado: The smooth uv at borders didnt change anything to be honest.
@ Morbid Angel :The baking with subdivision is more logic like you say indeed, I tried it and the result was a tiny tiny bit better.
The holes are still there unfortunately.

How is this possible? There is nothing special there must be a sollution i think.
any other ideas? I absultely want this to work...

its somehow giving up on this specific problem but is vector displacement an option?
I have dont my research at http://renderman.pixar.com/view/vector-displacements i can see the benefits but still does it replaces displacement, since its new?
Why would you still use displacement if you have this?
thanks again

[Morbid Angel]

I think its a known issue all around. It especially is prominent when uv's are round. If you for example take your uv borders and make them straight so snap them to grid i.e. 90 deg vertical and 0 deg horizontal then it should be a much better result. The logic being that you cannot properly divide a pixel on an angle since all pixels are square. You can also post your scene if you would like for us to give it a try.

[airion]

Hmm I dont understand what you mean exactly, but thanks for the suggestion.

Attached is the testfile, both max 2013 and max 2012
Curious to learn more on this problem...
Could you also pls ellaborate on my question regarding the vector displacement maps? Does this approach actually replaces displacement? Meaning its better on all fronts?

Test_001_max2012.zip
Test_001_max2013.zip

[Morbid Angel]

Hmm I dont understand what you mean exactly, but thanks for the suggestion.

Have a look at this scene. I also got the seam at first, look at the cap of the cylinder's uv's and the displacement map's filtering is set to 0.01 you also need to make sure you bleed the edge of the map far enough so filtering does not choke it in during rendering, that seems to solve this seam issue (in your scene you need to match the uvs)

https://www.dropbox.com/s/848g9ed6b3...max2013_dv.zip