Noise Reduction

Hey all. How would you reduce noise of a render and make it look clean before rendering and after? for example, I heard of a technique called bilateral blur, or something like that. the problem is, I can’t use it because I’m only doing a still image. I know that glossy and refraction shaders cause a lot of the noise in images, so how would I post process it with compositor? I just need anything that will reduce noise without overdoing the rendertime. thanks

It’s not an easy topic. There are many ways to reduce noise and the correct approach depends on the kind of noise you are facing and which render pass generates the noise.

You should start by combining the render passes manually in the compositor and try to reduce the noise on each pass individually.
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Passes

You can then decide if you need to increase the samples/bounces for some of the render passes or if you can get away by faking some effects. You can use the despecle node to get rid of caustics, the bilateral blur for diffuse noise and so on.

Sometimes it can also be helpful to activate ambient occlusion to get more light and less diffuse noise. Adding more light sources helps too.

If you use environment lighting you should active multiple importance sampling to reduce caustics. It can also help to enable “no caustics” or “filter glossy” if you can get away with it in your scene. There are also lots of settings for lamps which you can finetune to get better results.

As you can see, there are so many options to choose from, but the correct approach heavily depends on your scene. There is no general answer.

Make sure you watch Thomas Dingens Video from the Blender Conference: http://www.youtube.com/watch?v=ENy9TAskxt8

Thanks Temar for your lengthy and detailed response :slight_smile: Is it possible to reduce or eliminate noise by just rendering with a vast amount of samples?

In theory: yes

In real world scenarios however you have to bump up the amount of samples to a ridiculously high value which will lead to insane render times. If you don’t really want to get into the noise reduction topic, you can use one simple trick to improve your results: Just render your image with twice the resolution you are targeting (e.g. 3840x2160 instead of 1920x1080) and then scale it down afterwards. This will eliminate a lot of noise.

Ok thanks. It’s not that I don’t want to get into noise reduction, but my curiosity precedes me :slight_smile: