Get a Point Pass Postion Pass For Nuke?

[mayajunky]

Well there are two tags I've never actually used but maybe will get you heading in the right direction. The External Compositing tag and the Point Cache tag. Could be of some use.

[berandogan]

I too wonder.

[Per-Anders]

There is no pass specifically for that (though it would be easy to add), however you can generate one the simple old fashioned way: Just make a layer shader with three gradient shaders in add mode, set the gradients to linear interpolation one with red, one green, one blue, set their space to world and adjust them so that the red one goes long x, the green one along y and the blue one along z. Adjust them to cover the area of your scene as a box, i.e. the length of each gradient must be the same, apply to everything (possibly an env object for that) and save as at least a 16bit image.

Now I don't have Nuke so the next part is assumption that Nuke uses absolute values rather than a scene scale and adjusting itself, but in Nuke you'll have to de-normalize this data, so you'll multiply the output by the distance you put in to your gradients, and now you ahve a unit space value for each pixel. You may also if the gradients started a certain distance from world 0 have to add this value to the final output of this pass before making use of it.

[dirtyharry]

nice per,
but as i have used nuke and also tryed this way, nuke uses positive and negative values,
how would u do this in c4d?

dharry

[Per-Anders]

You can't with a gradient. As mentioned you'll have to factor the offset to world 0 from the start of the gradients in nuke after un-normalizing the pass, this will effectively create negative values as you'll be subtracting the start location of the gradients from the image value thus in certain areas possibly giving you negative values.

[WillRyan]

I have a feeling that with the release of Francois Tarlier's ft-PPass2Matte plug-in for After Effects (http://aescripts.com/ft-ppass2matte/), quite a few more people will be finding their way here. Any chance we could see you provide a scene file or a quick video tutorial, Per?

[throwstone]

I have followed Per Anders instructions to the best of my ability,
Attached is the shader I developed...
Could someone take a look and tell me if this is correct?
(If so this could become a good template for others attempting to achieve similar results!)
(http://dl.dropbox.com/u/792881/temp/PointPass.c4d)

[kosmogos]

might be a bit late but there's a plugin made by Michael Auerswald for this:
http://www.krautsourced.com/?p=142
Tried it and it works flawlessly in Nuke!