Hi fellas any help with the black dots on the render below? Found some info around the web but nothing helped me out (it was an old stuff in fact). Really dunno what could causing this...
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1$\begingroup$ Possible duplicate of blender.stackexchange.com/q/4980/599 $\endgroup$– gandalf3Commented Dec 26, 2018 at 3:41
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$\begingroup$ Hi Gandalf I know about this topic and already saw it but its something different cause I found out that the render getting worse with more lights despite they could not be seen (are behind walls in different rooms) so Im wondering why this is happening. $\endgroup$– Jan MatysCommented Dec 26, 2018 at 11:21
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$\begingroup$ Related blender.stackexchange.com/q/30407/599 $\endgroup$– gandalf3Commented Dec 27, 2018 at 3:53
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1 Answer
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By default cycles samples one lamp at a time. The black spots likely correspond to samples where cycles was attempting to sample lights which are doing nothing for actually illuminating the visible objects.
You could try disabling Multiple Importance Sampling on lamps/materials you know won't contribute much to illuminating the scene, and/or play with the Light Sampling Threshold in Properties > Render settings > Sampling.
However, if that doesn't cut it, then you can use the Branched Path Integrator, which allows for sampling all lights at once:
Note that it works a bit differently from the default integrator, so try playing around with the settings to see what works.
answered Dec 26, 2018 at 11:48
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$\begingroup$ THX mate already found out that BPT makes a better results but still try to "fiddling" it up. Light sampling threshold already tried but makes not much of a difference in my tests. Btw sampling one lamp at a time sounds "weird" somehow ... how its working in fact? $\endgroup$ Commented Dec 26, 2018 at 12:53
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$\begingroup$ Looks like its very useful in areas with even low light but in areas where is almost black (really dark) this BPT method is noisy as hell. $\endgroup$ Commented Dec 26, 2018 at 19:58
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$\begingroup$ @JanMatys I'm not too sure of the specifics beyond what brecht (the original author of cycles) said here: blender.stackexchange.com/a/23006/599. As for noise in really dark areas, you could try playing with sample all indirect lights. Whether it hurts or helps rather depends. $\endgroup$– gandalf3Commented Dec 27, 2018 at 3:53
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$\begingroup$ Playing? This could be turned on or off or ... am I missing something buddy? $\endgroup$ Commented Jan 8, 2019 at 10:06
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$\begingroup$ @JanMatys I mean making test renders with it on and off and observing the effects on noise/render time. $\endgroup$– gandalf3Commented Jan 9, 2019 at 2:45