I have a scene I want to render where a small object moves across the camera's field of view. The rest of the scene is just a black void containing absolutely nothing (see image below). I need to render this as an image sequence.

This object is basically a mirror reflecting a somewhat complex scene, so I want to render it with a very high resolution (14mpx or more). And enough samples to get a good quality on the reflections.

The problem is that if i rise the number of samples, and because of the high resolution, it takes ages for each frame to render, while most of the time is just spent rendering a black region. The camera must stay static during the whole sequence.

Is it possible to configure blender to use a high number of samples around the object, and a very low value on the empty region? (I want to make the whole process faster)

enter image description here


I used the option border in the render menu, as described in this answer

  • 2
    $\begingroup$ You might be interested in this article on Greg Zaal's blog. $\endgroup$
    – PGmath
    Commented Nov 21, 2014 at 16:27
  • $\begingroup$ @NoviceInDisguiseGraphics - I tried this but without success. Apparently, the pixel color information (or lack of) comes as an output after the pixel has been raycast, but all of the samples are still used even when there's nothing there. $\endgroup$
    – ButterDog
    Commented Nov 21, 2014 at 18:08
  • $\begingroup$ @PGmath - That looks exactly like something it could help. Thanks. $\endgroup$
    – ButterDog
    Commented Nov 21, 2014 at 18:09
  • $\begingroup$ You could also try using Branched Path Tracing, and have a higher number of reflection rays. $\endgroup$ Commented Nov 21, 2014 at 19:29

1 Answer 1


Adaptive sampling is now an integration added to the 2.8x series, and you can enable this by going to the render properties panel (the camera icon), and checking the box for "Adaptive sampling" underneath the Sampling tab.


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