I'm trying to get an accurate index pass for compositing. My geometry (a window in this case) consists of straight lines and it would be nice to have a perfect mask for color correction. As you can see Anti-Aliasing is enabled, but there are still some weird pixels:

enter image description here

Until now my workaround was to blur the image, but in this case straight lines are key to work with. How to achieve this? Is there a render setting to prevent the noise or make it less noisy?

  • $\begingroup$ add a additional layer that has nothing but the index pass, and see if its output is better $\endgroup$ – Chebhou Apr 24 '15 at 18:51
  • $\begingroup$ Thanks @Chebhou. Already tried, but this can't be a permanent solution. What if I need more than 20 id passes? $\endgroup$ – p2or Apr 24 '15 at 19:06
  • $\begingroup$ you would use one layer just for index pass ( one layer for all indexes ), not each object or material with its layer $\endgroup$ – Chebhou Apr 24 '15 at 19:07
  • $\begingroup$ @Chebhou Mhhh. I'm searching for a solid solution - using IndexOB makes more sense than using render layers. $\endgroup$ – p2or Apr 24 '15 at 19:17
  • $\begingroup$ is that what you have tried ? $\endgroup$ – Chebhou Apr 24 '15 at 19:22

You will have to render without DOF, and add it in during compositing in order to get clean IndexOB masks. Otherwise you'll probably have to separate via layers if you want in-camera DOF.

Alternatively, you could try this solution, which creates a second Scene, linked to your main scene with the camera DOF turned off. That way your second scene would have IndexOB masks with clean edges, and you can work with both scenes in the compositor. Would that solve your issue?

I'd be interested to know your final pipeline, I'm dubious that the clean masks would help you modify your DOF renders, but I would be interested to see more about it if it can.

  • $\begingroup$ Thanks Todd :) The image above almost has no depth, it's a really bright scene and F-Stop is at ca. 8, but it seems that this setting has a major impact. As I said, I ever thought index ob passes ignores the depth settings, because it's only a black and white calculation and gradients are not supported. In this context it makes no sense to provide this feature at all, but maybe it's not complete... I don't know if it's mathematically possible to calculate soft transitions like a mist pass, but I think we can create a cycles shader for this case. I'll try and let you know. Thanks again. $\endgroup$ – p2or Apr 27 '15 at 8:08

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