Adaptive subdiv tears mesh apart along uv seams
Open, NormalPublic


System Information
Debian testing, Nvidia GTX 780

Blender Version
Broken: 2.78 RC2

Short description of error
Adaptive subdiv tears mesh apart along uv seams even if adaptive is unchecked.
There are four phases:

  1. Adaptive enabled and displacement set to both -> huge tearing
  2. Adaptive enabled and displacement set to both -> huge tearing (differs a bit)
  3. Adaptive disabled and displacement set to both -> thin tearing and small holes in some uv corners
  4. Adaptive disabled and displacement set to true -> no tearing and bigger holes in some uv corners

Exact steps for others to reproduce the error
Open the file and hit render in four different conditions.

I think the problem is in the difference in UV smoothing while baking the map and while rendering.
When you bake a displacement map, you are using the only available method for UV smoothing - vertex with valence of 2 is considered a corner and not being smoothed, while all the other valences ARE being smoothed. And I consider it the rightest way to smooth UV, by the way.
On the other hand, when we render, we use one of the OpenSubdiv's method for UV smoothing and it's hidden under the hood. You guys tell me which method it is.
For example, Renderman, Maya, Mudbox, etc have the option to choose the UV subdivision method, which leads to a ton of problems (on our studio, for example), by the way, when you need to synchronize the smoothing method while sculpting and while rendering. But it would be very nice to have this kind of option to choose in Blender.

I hope i'm not mistaken.

Thank you.


To Do
Sergey Sharybin (sergey) triaged this task as Normal priority.Sep 23 2016, 9:47 AM

Here's one more evidence.
It looks like adaptive subdiv doesn't smooth uv's borders at all. The texture has a perfect white circle and it should look like on the left cylinder.

subdivide uvs is not supported at the moment (thats why its grayed out :))

Oh, that's a shame. It makes adaptive subdiv useless, unless you don't use uv subdivision across all of your objects while sculpting and texturing, which is not a common practice. Or you just don't have uv seams

Brecht Van Lommel (brecht) edited projects, added Cycles; removed BF Blender.EditedSep 25 2016, 2:02 AM
Brecht Van Lommel (brecht) changed Type from Bug to To Do.

Smooth UV subdivision is indeed missing still. Of course it's important but that's why this feature is marked Experimental, it's unfinished.

It surely is experimental, but it's a huge game changer, and I just can't wait to use it throughout my projects. That's why i'm testing and reporting issues so bad:) And many people already treat it as a killer feature and make reviews, such as Andrew Price.
Anyways, thank you for your hard work!

Hi, I don't know what is the status of this task but I will join Yegor in saying that this feature would have a huge positive impact on my workflow. I would even qualify this as paramount, it alone would open a world of new possibilities in my work. I do archeological reconstruction and restitution and the ability to use a uv displacement map with adaptative subdivision would allow an unprecedented level of detail across the entire model without worrying too much about performance. I can't wait to see this feature fixed and implemented! Thanks for your consideration.