Masks in comp, wire color, fringing

[chroma]

I was wondering if anyone could elaborate on a best practice regarding how to perfectly select, for an example a tree, in comp using a renderpass?

The wirecolor is perfect, except that it makes it impossible to select things without missing on the tolerance factor, and hence it's making ugly edges and not filling my needs anyway. Perhaps I'm not doing it right.

How do other people solve that?

[Morne]

use multimatte and render against black background. Whatever you you had as background for example vraysun or hdri, should be put into the vray environment override

multimatte can use either material id or object id. The multimatte can give you 3 masks at same time, one for each R G and B channel and it makes for perfect masks (when rendered against black for example)

You could have the entire tree in the blue channel, or you can have the fruit in red, the leaves in green and the trunk in blue

[chroma]

Ok thanks for answer. So the real trick with this that does not apply with wirecolor is the black background, right? So per definition the wirecolor could be used as well, if the object was isolated. But with multimatte use, there's no need to rerender to get black backgrounds.

[instinct]

This still would not be "perfect" as you requested above. There is a mix of different samples in every pixel. And these may be from different objects. So if you have a single color value that is a mix of two objects' colors you can not perfectly select them with a mask. You can when rendering to deep and selecting things via Object ID on the sample level. We do this for our (car/product) configurator work.

[chroma]

... You can when rendering to deep and selecting things via Object ID on the sample level. ...

Interesting. Rendering to deep = rendering to 32 bit exr?
Object ID on sample level. How's that done? I'm aware of the Object ID selector in the object preferences, and the ObjectID render pass, but what do you mean with on sample level?

I'm interested in learning more about this!

[Vizioen]

Interesting. Rendering to deep = rendering to 32 bit exr?
Object ID on sample level. How's that done? I'm aware of the Object ID selector in the object preferences, and the ObjectID render pass, but what do you mean with on sample level?

I'm interested in learning more about this!

Not quite: https://docs.chaosgroup.com/display/...Output+Support

[dgruwier]

Bit depth just the precision of the colors. Better precision, fewer artifacts. 32-bit can be useful for some utility passes where small flaws can create visible artifacts, but for simple selection mattes, 16-bit should be plenty.

Deep is a seperate rendering technology. Just looking at a pixel, you can't "unmix" it to find out out many objects contributed to it or how. With deep, each pixel has a depth value, and you can have multiple pixels at multiple depths layered on top of each other. That way you can pick out half transparent overlapping objects from each other and manipulate them individually.

Incidentally, 32-bit precision can be necessary for the aforementioned depth information in Deep renders, but I think that happens automatically.

[leon0101]

I was wondering if anyone could elaborate on a best practice regarding how to perfectly select, for an example a tree, in comp using a renderpass?

Try using either Object ID or Material ID. Turn on 'Enable Filtering' and change output type from 'Integer (no AA)' to 'color (with AA)'. This will add anti-aliasing to the render pass and you should find it easier to mask.

The other solution is in photoshop using select and mask, like this:

https://www.youtube.com/watch?v=uJZIwdbWFuc

These are the tools we use in the office. I hope this helps.

Best, Tom