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I'm very new to blender and I just managed to get the result I'd like to have, but when I render my image with the Cycles Render the light reflections will rendered black instead of shiny white as I'd expect them too.

Does anyone have an idea why this happens and can point me in the right direction for a solution?

enter image description here

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  • $\begingroup$ try to add your file. $\endgroup$ – user219279 Feb 26 '18 at 14:00
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    $\begingroup$ Don't use clamp direct (or set it to a value that is just a bit lower than the intensity of your lights). blender.stackexchange.com/questions/45195/…. $\endgroup$ – user1853 Feb 26 '18 at 14:07
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    $\begingroup$ what do you have as a world texture for it to reflect off of? If your world is black, then you will see black reflections. $\endgroup$ – David Feb 26 '18 at 15:09
  • $\begingroup$ @cegaton, I added the clamping issue in my answer, as well as several other optimization issues. Could you take a look in case I missed something? $\endgroup$ – yann Feb 26 '18 at 15:13
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The mistake is in your shader. You are mixing two glass shaders depending on the viewing angle. This causes the physically incorrect resut. Strip out the dark glass, the mix shader and the layer weight node and everything renders fine.

enter image description here

Edit

There are comments mentioning poor rendering optimization, so I took a closer look at your file and reduced the rendertime from estimated 1,5 h to just over 14 minutes at 5760 x 3240 pixel.

The changes:

  • replaced all mesh lights with area and point lamps, they are much less expensive to compute (less noise)
  • deactivated the direct and indirect clamping. This reveals, that your lights are way too bright and cause the reflections to blow out. reduced all lamps so the reflection values stay below 1.
  • deactivated "progressive refine", this slows down your final render significantly
  • raised tile size to 1024 x 1024 pixel (this might be GPU-dependent and slower on your machine, you might leave it at 512 px².
  • reduced samples to 512. Without the mesh lights we can get away with less samples
  • deactivated denoising, it is not necessary here, imho. The image is virtually noise free after 512 samples.

The optimized .blend: enter image description here

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  • $\begingroup$ I really appreciate your detailed and updated answer as it really helps me moving forward with learning Blender! :) $\endgroup$ – mxmtsk Feb 26 '18 at 15:52

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