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I have a bunch of glossy balloons lit by a sun lamp and the world (Background Sky Texture). This is the nodes setup.

enter image description here

After rendering I have the image below.

enter image description here

When we look at a more detailed level we see a lot of noise / fireflies.

enter image description here

I already enlarged the size of my sun lamp, set the samples at 1000 and the Filter Glossy at 10. Still noisy image. Also unchecking caustics did not solve the problem.

Changing the clamp settings does not look like a solution, given the nature of the image. AS I understand it I can only try with extremely large settings for samples. Or is there any other solution to get rid of the noise and keeping the highlights in the image ? Or should I look for solutions outside of Cycles ?

Here is my file

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  • $\begingroup$ Did you use Multiple Importance Sampling? $\endgroup$ – VRM Oct 14 '15 at 15:59
  • $\begingroup$ No, I thought that is only possible with HDR images ? $\endgroup$ – Old Man Oct 14 '15 at 16:00
  • $\begingroup$ I am now rendering with MIS, Filter Glossy = 10 and 1000 samples but it does not look like that the noise is gone. $\endgroup$ – Old Man Oct 14 '15 at 16:19
  • $\begingroup$ At the moment the best solution I can find is a combination of 1) enlarging the size of the lamp 2) using Filter Glossy (setting = 1) 3) trying to find a balance in number of samples and clamp setting $\endgroup$ – Old Man Oct 15 '15 at 8:53
  • $\begingroup$ I'm trying to replicate your setup, nodes and basic baloon shapes. I have a sun of size 1, but can't reproduce those shiny specular on baloons... can you sahre the light type, position and setup? $\endgroup$ – m.ardito Oct 15 '15 at 11:30
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A few things to try when dealing with fireflies:

Enable Multiple Importance in your light:

enter image description here

Left is your original settings, right with Multiple importance enabled. (click on the images to enlarge)

enter image description here

Using clamp indirect takes care of most of the fireflies with no noticeable side effects as far as I can see...

enter image description here

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Now for a super clean render you might want to use Branched Path Tracing:

enter image description here

enter image description here

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  • $\begingroup$ On a side note, I noticed you are using GPU rendering but have the tiles set to a very small size. Modern GPUs work better with larger tiles. Depending on your configuration you might want to try a tile size of 128 or even 256 pixels. $\endgroup$ – cegaton Oct 16 '15 at 15:22
  • $\begingroup$ Really, thanks a lot !!! A few remarks ... I thought that Multiple Importance was (only) effective for HDR lighting ? I read that at a Blenderguru post about noise reduction. You use only the indirect clamping ? So .. does this mean that the noise is mainly caused by indirect light ? Last ... I have to read more about branched path tracing, new for me. Thanks !! $\endgroup$ – Old Man Oct 17 '15 at 6:50
  • $\begingroup$ about the tiles and GPU rendering. I render on a windows desktop with a nvidia gtx 970 gpu. Does this say something about the tile size ? $\endgroup$ – Old Man Oct 17 '15 at 6:55
  • $\begingroup$ @JanScherders multiple importance affects all emitters (not exclusively HDR) read: blender.stackexchange.com/questions/8152/… and blender.stackexchange.com/questions/5309/… $\endgroup$ – cegaton Oct 17 '15 at 14:58
  • $\begingroup$ As for the size for render tiles, don't go with someone one else's recipe, do make a few tests to determine the optimal size for your system. It does vary with the complexity of the scene as well. In gentral to render a frame in HD (1920x1080 ) the best performance I get is with tiles of 240 x 270 pixels, (on two GTX780), but your system might be different. $\endgroup$ – cegaton Oct 17 '15 at 15:16
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I post here to attach an image of scene asI was able to reproduce (see comments above)

enter image description here

And I get almost no fireflies/noise:

enter image description here

edit: now I just reduced my sun from 1.0 to 0.1 and I get also similar shiny specular... image is more noisy, though, but I don't see fireflies...

enter image description here

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  • $\begingroup$ hi I have a sun lamp with size = 0.1 at the right (and that gives the specular highlights). I also have a world background (sky texture) that gives a backlight. I thought that clamping is only bad news but after doing some renders I find that when you you set clamping at for instance 3 and enough samples the fireflies are gone. I had expected that clamping destroys the image but that is not the case. $\endgroup$ – Old Man Oct 15 '15 at 21:27
  • $\begingroup$ sorry, forgot to add my file. file is now added $\endgroup$ – Old Man Oct 16 '15 at 14:27

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