Why Blender Cycles puts some white dots in the image?


(Michael George) #1

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Actually, this is the first time to use Cycles and I can see that there are a lot of white points or dots in the rendered image.

I wonder why this happens? and how can I remove them and get a clear image?


(ajarosz) #2

t’s not only cycles thing. It is just a noise and this type of noise is called often here fireflies. When you use caustics in reflection/refraction there is a lot of noise. So, more samples and turn off caustics. If you don’t want to turn off caustics you needd to use like a lot more samples or filter glass/use some clamp.


(Emir Sinan Gürlek) #3

Take a look at this: 7 Ways to Get Rid of Fireflies Once and For All


(sundialsvc4) #4

I’ve pondered for a long time: “what is it about the Cycles algorithm that causes fireflies?” Did the algorithm simply fail to find a light-source for a particular pixel, so it “left it ‘blank?’” If so, then why are the fireflies always small? And always white, not black?

I know that we find various ways to prevent them and/or to compensate for them when they occur, but why, technically, does this [set of] algorithm[s] produce them at all?


(kesonmis) #5

Simplified example: you have a surface that is somewhat rough but reflective, and a small but strong light source. Render with one sample. Each pixel of that surface either reflects that light or not. As ray direction is random, most pixels are black because that one sample ray does not hit light source. Some are very bright because they do hit the light. These look like fireflies. The more samples you add, the more neighbouring pixel values converge. But if light paths that cause bright lighting are very scarse (caustics, light through small holes etc), fireflies need a lot of samples to average out.