I'm trying to render a glassy flac. The problem is, taht it makes black reflections on sides or corners. I don't know where these reflections come from, almost white world and in the example the flac is in white cube and still there is black left side.

What can I do to get rid of these black spots?


  • 1
    $\begingroup$ I think this is not reflections, but due to refraction! What value did you set for the "IOR" value of the glass shader? I suggest you to try with a value closer 1.0. $\endgroup$
    – Polosson
    Sep 25, 2014 at 10:21
  • $\begingroup$ I used 1.51714 as suggested here link. When I get to 1.2 it's almost gone, but also some of desired details disappear. $\endgroup$
    – Magorr
    Sep 25, 2014 at 10:48
  • 1
    $\begingroup$ blender.stackexchange.com/questions/2558/… $\endgroup$
    – Omar Emara
    Sep 25, 2014 at 11:29
  • $\begingroup$ These are probably shadows from the light. The only way I've found to get rid of this is to disable them. $\endgroup$ Sep 25, 2014 at 17:04
  • 3
    $\begingroup$ Looks to me like a combination of total internal reflection and not enough transmission bounces. Note that this is in someways correct, as if light bounces around inside a piece of glass far enough, it will be absorbed pretty much completely. See e.g. these images $\endgroup$
    – gandalf3
    Sep 25, 2014 at 17:10

3 Answers 3


In the render properties for cycle find the Light Paths and increase the Transmission value till the dark spots go away.


I had the same issue and found it was due to my glass being shaded smooth. I added an Edge Split modifier and the black areas of refraction went away.


Use transparent instead of glossy when the glossy ray depth is grater than the value of max glossy bounces.nodes


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