FBX import for PPP - everything thrown into one UV-set

[ajz3d]

Hi.
I have a problem with my new 3D-Coat->Houdini pipeline.

Because 3D-Coat's subdivision isn't compatible with any of subdivision algorithms utilised by Mantra (Mantra CC and OpenSubdiv CC), 3D-Coat's and Houdini's smoothed UVs don't match. This means that I will get unacceptably distorted textures if I bake them in 3D-Coat and render in Mantra. On some denser objects, the distortion is barely visible, but it is still there.

So, seeing this, I resorted to a good old method of importing pre-subdivided objects to paint room. However even though my FBX contains several materials (one uv-set per material) and objects, 3D-Coat upon import merges all UV-sets into one, which it calls: a "uv", and then stacks all UVs in that single tile. What's interesting, is that the list of "Surface Materials" does contain all my materials (there's nothing wrong with the list of objects as well).

This is the thing that I do not understand.

If 3D-Coat recognises my materials, then why does it throw UVs of all objects into this single UV-set, and at the same time keeps the list of materials intact? Frankly, that's the first time I meet with something like this in 3D-Coat.

What can I do to prevent this from happening?

Edited February 13, 2015 by ajz3d

[digman]

Can you share the FBX model?

Do you have import as tiles selected by mistake,  I know it is a dummy question to an experience user so forgive me for asking...

[Javis]

Hey man.

 

Yeah, this is a problem. It's because 3DC doesn't know how to treat different materials with the same UV map name. The easiest way around this, is to use different UV tiles for each material. I know, not elegant, but it's the best way. Just make sure to turn on "Import Tiles as UV Sets" and then export "UV Sets as Tiles". That feature might be named different depending on the build you have, in the latest build it should be called something like "Import Tiles as UDIM".

 

Just note that you'll have multiple UV maps when you export doing this. Unfortunately. But you can combine then in Houdini I'm sure. I do this in Modo too.

 

 

A side note relating to SubDs for UVs. 3DC always imports meshes with all UV maps as linear UVs. I don't know about Houdini, but in Modo there is a function that lets you always use linear UVs, even if the UV map is SubDs. If it does, that should save you a little trouble there as well.

[ajz3d]

Hey guys!

Do you have import as tiles selected by mistake(...)

Digman, actually I tried the opposite, but forgot about the necessity of creating tiles out of my UVs.

 

I know, not elegant, but it's the best way. Just make sure to turn on "Import Tiles as UV Sets" and then export "UV Sets as Tiles". That feature might be named different depending on the build you have, in the latest build it should be called something like "Import Tiles as UDIM".

Elegant or not, the important thing is that it works! Many thanks.

 

A side note relating to SubDs for UVs. 3DC always imports meshes with all UV maps as linear UVs.

I don't know about Houdini, but in Modo there is a function that lets you always use linear UVs, even if the UV map is SubDs. If it does, that should save you a little trouble there as well.

It's possible with subdivide SOP. Houdini and OpenSubdiv Catmull-Clark algorithms do have options that allow for keeping UVs linear. However adaptive subdivision at rendertime doesn't have any customizable options apart of algorithm selection (Mantra Compatible CC and OpenSubdiv CC), and this form of subdivision I use for rendering.

I have doubts about using linear UVs on subdivision surfaces. I was always convinced that they're the main and most obvious cause of texture distortion and artifacts. Especially on non-organic subdiv models?

Thanks, guys.

Edited February 13, 2015 by ajz3d