UV Render Pass

[loudsubs]

How do you setup a UV render pass in Houdini?

The new 3D World has a tip about how you can use a "UV Pass" pass in Nuke with the STMap node to tweak already rendered textures and add more detail without having to go back to 3D. Sounds pretty useful. Anyone have info on this?

[Annon]

In your Mantra node's "command" field (in main tab) enter this:

mantra -u /obj/geometry

Where "/obj/geometry" is the geometry node you want to render (don't think it goes into SOP level nodes, but not 100% on that.

That will render in UV space, so make sure you have UVs attached as a vertex attribute.

You don't have to jump into Nuke to make edits. Try Houdini's comp context. /img

Hope that helps

Christian

[jim c]

One thing to note, at least this is what I found, you must NOT have overlapping UV's or the texture that's rendered will be borked - it will look like crap. I found that if the mesh was NOT polygonal, then this didn't work very well. I recall trying to render out texture from a NURBs surface and ran into problems.

[loudsubs]

Good to know. I'll give it a try. Thanks

[Ryan]

I just finished using this myself. Make sure your geometry is polygons and your UV attributes are vertex type, not point type. As mentioned by jim c, NURBS won't work, not even Curves.

You can choose your geometry in the Mantra node in Properties->Render and set the UV Render Object. As mentioned by Christian, it stops at Object level. I found it best if your UVs are kept within a 0 to 1 range and then you render a square output, like 2048x2048, because the STMap node in Nuke will stretch the pixels a but when mapping. The UV render will also get any color attributes you have too.

A quick Nuke tip: After your UV pass, you can use a Grade node and use the offset and multiply values to move your texture along the object.

Edited November 2, 2011 by Ryan

[Naeem]

Hi! I am trying to create a UV render pass - in my scene I just have a simple grid and a simple Mantra Surface Shader applied to the grid with a UV Texture node with Apply To set to Vertex texture. But it's not working for me. Anyone have a working setup in a scene file?

P.S. : My out node is set correctly with UV Render Object set to the grid and UV attribute set to UV.

Edited July 11, 2013 by Naeem

[Naeem]

A scene file.

od_UV_Render.hip

[anim]

I wonder what does UV render object have to do with UV pass or the original question?

to make UV pass, just export UVs from your shaders using Parameter or Bind VOP as you can do with any data

and use that variable in Mantra ROP

see the file, change to uv image plane in render

uv_deep_raster_pass.hip

[Naeem]

Hi Tomas, good to hear from you again and thanks for the file.

I think there was some confusion in the thread between rendering in UV space and rendering UV passes. I see the method you've shown is very straight forward and makes sense. Thanks again.