View Full Version : STMap Workflow

05 May 2010, 06:27 PM
Has anyone found a good workflow with the STMap node in nuke? I'm a compositing student nearing the end of Full Sail and tried to use it last month on a project, I had some buildings that I rendered out on surface shaders in Maya and was doing all the lighting in Nuke using other passes I had rendered.

Since the buildings were just on surface shaders with no lighting information, tweaking and updating the texturing in Nuke would have been faster and easier than re-rendering them out of maya if there were any changes.

So I rendered out a UV pass from maya and only got the texture mapping to work well if the UV pass didn't have AA, but since its essentially using the UV pass as the edges of the geometry, that didn't really work well either because the edges were aliased. Is there something I'm missing or haven't thought about?

Thanks in advance

05 May 2010, 06:57 PM
Make sure the UV pass your getting is 32 bit float.

05 May 2010, 10:59 PM
Is there something I'm missing or haven't thought about?

Yes-- that it never really works well. There are a million pitfalls to 2.5 retouching.

1) No overlapping objects.
2) Always do it on an unpremultiplied image.
3) You won't get any texture filtering.
4) It never really works perfectly and should only be used in very specific places or for pre-viz which you then re-render in the real 3D scene, or Nuke's scanline renderer.

- If you have two objects overlapping the AA will sample between the two and you'll get a blended UV position which is completely wrong.

- If you have a premultiplied image the edges will be blending between 0,0 and the correct UV position.

- An STMap can only ever be *a single* pixel. You can't have an STMap which is the average of multiple UVs. If you are looking at an oblique plane then you'll just render the average UV position which would be the middle of the map. A 3D render will filter the map so that the RGB color is the average of the entire map.

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05 May 2010, 10:59 PM
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