enter image description herehttps://i.sstatic.net/twSI1.jpg

How do i fix the firefly type artifacts? None of the leaves have a glossy surface so that shouldn't be causing the problem?

Here's a file of just the front tree. (sorry for the file size) Updated version. https://www.dropbox.com/s/5m46lz9vzqehhh7/Toussaint%20-%20Copy.blend?dl=0

enter image description here

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    $\begingroup$ Shaders shouldn't affect the Z-pass. It looks to me that what you are facing is some kind of Z precision error. Try limiting the near and far clipping distances for the camera, so that the clipping starts at the closest object and ends at the farthest one. $\endgroup$
    – user1853
    Commented Jun 16, 2016 at 17:52
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    $\begingroup$ I don't think they are fireflies. Those same spots are in the color render too. Maybe reflections or highlights... Nice job BTW $\endgroup$
    – Dontwalk
    Commented Jun 16, 2016 at 18:25
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    $\begingroup$ Does the second picture contain some post-processing with the faulty z-buffer? The leaves look weird where there is an error in the z-buffer. If not, try fixing this on your model. $\endgroup$
    – piegames
    Commented Jun 16, 2016 at 18:27
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    $\begingroup$ Would it be possible to post a blend with just the foreground bush to let us see the error up close? That would be helpful. Also a screenshot of your comp nodes would be good too. $\endgroup$ Commented Jun 16, 2016 at 22:29
  • $\begingroup$ @elmo274 It would be helpful if you posted a file that contains the tree that is close to the camera and the object that is the farthest away. Otherwise is hard to determine precision issues. $\endgroup$
    – user1853
    Commented Jun 17, 2016 at 1:34

1 Answer 1


Glossy shaders won't affect the z-pass at all. The z-pass is literally a gray-scale of how far away each pixel is.

The answer to this question is exactly the same as any other question dealing with Cycles noise (though it might not seem like it at first). Noise in regular renders is a precision issue, and the noise here is also a precision issue. The way that Cycles improves precision is with more samples.

It's slightly different with the z-pass in that there's not nearly as many contributing factors to "how far away is this pixel" as there are to "what color is this pixel." But there are some. The main contributor is likely anti-aliasing. But even then, the solution should be the same: render more samples.

cegaton's recommendation to adjust the near and far clipping planes, is also a good idea.

If that doesn't help... well, I may just be mistaken... and that's okay.

  • 4
    $\begingroup$ Please read this: blender.stackexchange.com/questions/36072/…. This answer is wrong. $\endgroup$ Commented Jun 16, 2016 at 18:44
  • $\begingroup$ Excellent comment. I did not expect that to be the case. I'm interested to experiment with rendering a couple of these with different seeds and stacking them... $\endgroup$
    – Matt
    Commented Jun 16, 2016 at 18:46

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