Negative UV Space <uvtiles> and layered shader

[syrez]

Hi,
we are evaluating Maya 2012 2.2 Vray demo here at the studio.

I currently have an object built in 3dcoat, zbrush, with 20 uvtiles in 4k resolution, color, normal map and displacement.

But now i get problems using the <uvtiles> and or layered shader setup.

First of, <uvtiles> does not seem to support a negative uv space.. like u0_v-1. For debugging reason, i splitted my mesh into seperate parts.

Vray recognizes the u0_v-1 space as u0_v0 and therefore loads the wrong map. So i went for a layered shader setup, where i manually blend all maps with the use of a layered texture in maya and transforming all my uv spaces in the placement node manually.

But the layered shader clamps all negative 32bit data.

I would now consider to rename all my files and move all my uvtiles into positive space in Maya, but for every change i would do in 3dcoat and Zbrush, i would have to rename the textures again and again. I can not change the uv's in these packages as far in production now, as HD geometry won't let me (zbrush) and microvertex painting either (3dcoat).

cheers and thanks

Patrick

[syrez]

Okay, now got another workaround, i just offset all my maps into positive color space +2.5 and then shift it down in vray afterwards.

[vlado]

First of, <uvtiles> does not seem to support a negative uv space.. like u0_v-1.

You are correct; we don't support negative tiles.

But the layered shader clamps all negative 32bit data.

I'm not sure if this could be it, but there is an option "Allow negative shader colors" in the V-Ray "misc" settings.

Best regards,
Vlado

[syrez]

Okay, thanks, for further projects and UV creation i will take that into account

Already activated negative shader colors in both render settings as well as file node. Does not work with layered texture.

Well, my work around works, gladly . Next time with proper UV for Vray i would just use <uvtile> and would not have to blend all maps.


I also got another thing i found, the model is going to be tree and i textured around 250000 simple poly planes with a double sided material. When i have an alpha for Opacity map with Filter set to quadratic, which is standard in maya if you import something. GI render time increase from 6 minutes to an hour. But in extreme closeup you don't see any difference with filter set to off, seems to me like vray does not even care about it. In a normal Advanced Material theres no rendertime increase with filter set on or off.

Strange, anyway, i just turn it off. But took me some hours to find out.

Thx again!
best regards

Patrick