In upcoming Blender 2.79, “Denoising” will be added as a new feature. The official wiki page is Dev:Ref/Release Notes/2.79/Cycles – BlenderWiki.
Denoising can remove “firefly” noise after rendering in cycle.
The firefly noise often occur in low sample size rendering, but I think the most problematic shader making many firefly noises is “subsurface scattering”.
So I tested subsurface scattering material on rice to remove firefly noise.
The video above shows summary of the test, although denoising in 2.79 doesn’t recommend animation use.
No Denoising Result:
First, these are not applied with denoising.
The 10 sample image was rendered in only 32 seconds. But it has many noises on rice.
The 100 sample image has less noises than 10 sample. But there are still noises. And rendering time is 4:30; much longer.
Default Denoising setting:
The 10 sample with Denoising removes almost all noises on rice. And the rendering time is 1:30.
It better than 100 sample with no denoising in cleanliness and rendering time.
The image below shows comparison of denoising and no-denoising with 10 sample.
Radius is size of area for denoising. Higher value of radius seems to remove many noises. Default value was good.
But radius=1 made the weird shadow on the rice like below.
Strength = 0.5-1 seems not to make much different result. But Strength=0 makes weird noise in parts.
Higher value remove more detail of image. Feature Strength = 1 makes painting-look result as the image below.