Displacement rendering subdivision patterns

[timmwagener]

Hi guys,

i have some 32bit displacement maps from ZBrush and so far they are rendering correctly in Vray.
But there are two problems:

1.On some round areas there are visible subdivision patterns like in the image:


Increasing Max subdivs or lowering Edge Length on the Vray Displacement set do not help.
Its not like the higher i go with the subdivs the smaller the pattern gets.....

2. The seems between uv islands are visible, even though Keep Continuity is on...

Here is a Screenshot of my setting:


Ideas or solutions are really appreciated!!!

Thanks,
Timm

[joconnell]

What does the base geo of your object look like in terms of it's topology?

[timmwagener]

Well actually, the first problem with the subdivision patterns is solved. Our ZBrush artist just put out a 4k map yesterday night, instead of the usual 8k ....patterns are much smaller now and borders round.

But the seams still exist and another problem appeared:

The are ugly borders on the mesh, even where there are no uv seams. I think its somehow related to uv distortion but cannot quite figure out why:


-


Any ideas? We use internal smoothing of UVs since thats what ZBrush does.The border thats visible in the render ins't directly related to a uv seam.

Do you guys have any experience with vector displacements in VRay from ZBrush. Would you recommend it over standard displacements for production?

[joconnell]

Hmm - I wonder is it even something to do with the difference in sizes between the various faces in terms of how it subdivides? There's a keep continuity option in the vray to deal with smoothing over surfaces but it looks like one of your vertices in the two bottom corners aren't welded and it's causing a break. On the vector front as far as I know there's some problems with the code in dealing with zbrush maps and Vlado is looking into it.

[timmwagener]

Hmm - I wonder is it even something to do with the difference in sizes between the various faces in terms of how it subdivides? There's a keep continuity option in the vray to deal with smoothing over surfaces but it looks like one of your vertices in the two bottom corners aren't welded and it's causing a break. On the vector front as far as I know there's some problems with the code in dealing with zbrush maps and Vlado is looking into it.

I think apart from probably the difference in sizes i couldnt image what should be wrong with the mesh.
I attached a render with the mesh subdivided by maya to subdiv level 2 and the displacement map in the color slot (displacement rendering off), which looks correct to me:


Edit: Keep continuity is checked on...theres an image of my vray displacement setting at the first post.
Edit2: Vertex and Face Normals, Tangents etc. seem correct there as well. Tried every possible combination.

[Morbid Angel]

Did you try it in MR? can you post this object and its displ map here so we can look.

[timmwagener]

Did you try it in MR? can you post this object and its displ map here so we can look.

Yeah sure, i would really appreciate if some experts here took a look !!
Here is a zip with a clean .obj of the object, the 32bit displacement texture, and a maya 2012 scene file with just my setup: http://www.kiiia.com/files/misc/vray...entProblem.zip
The Vray version is: 2.20.01

Thx a lot.

[vlado]

Assign V-Ray texture filtering attributes to the File node and set the "Smooth method" to bicubic or biquadratic. This should fix the artifacts.

Bilinear interpolation (the default):


Bicubic interpolation:


Best regards,
Vlado

[Morbid Angel]

Ditto...Vlado beat me to it By the way the exr has to be mipmapped. Sorry if it is already.

[timmwagener]

Hey guys, thanks for your answers!
Tonight i will have a look at it again and post the results!
Btw. in the Nuke write node settings i cannot find an option for MipMapping when in .exr mode. Where could i export them mipmapped or is mipmapping a default setting for exr when saving in Nuke?

[Morbid Angel]

Nuke does not do mipmapping I believe you have to use vrimg2exr converter and mip map there.

[timmwagener]

Hey guys,

the ugly border on the round area is gone now......the thing that did the trick was to put the base model one subdivision higher.
It was somehow related to how the uvs distorted on the areas where the border of the uv shells were preserved when smoothing.
So we are now at a stage where there are no borders anymore at areas of the mesh that have no seam

The next thing to target are the seams that actually are MUCH better now, but still visible....since production is pressed right now i will take an hour tonight to check that out!