very grainy

[Falcon]

Why is this image so grainy? I stopped the render, which is why there are black areas (not a bug).

Notice the grain in the clouds and in front of the mountain to the right.

Render Settings:
Detail 0.75
AA 4

64 atmosphere samples
ray traced shadows
cloud quality between 0.4 and 0.8 (depending on the layer, there are 6 layers of clouds in this image)
all cloud layers are set to no acceleration

[domdib]

It may be because your clouds are casting rays, which seem to show up grain. Incidentally, you don't need ray traced shadows in the atmosphere on except  when the sun is behind the landscape (and there may be one other unusual circumstance). My initial suggestion, switch this off, and re-render with higher atmo samples.

P.S. the clouds look great!

[Falcon]

Yes, that helped a lot. There is still the grain in front of the mountains, which might be the result of using fill lights instead of GI. But the grain in the clouds is gone now.

[Henry Blewer]

The grain in front of your mountains is atmosphere grain. I would try setting the atmosphere samples to 128.

[Tangled-Universe]

The grain in front of your mountains is atmosphere grain. I would try setting the atmosphere samples to 128.

Correct. I'd first render a crop with 96 samples and see if that's ok, but I also think that in the end 128 will give the best result probably.

The reason why some clouds, not all, are grainy is because you have the quality setting ranging from 0.4 to 0.8.
The ones around 0.8 are almost free of grain, the ones with quality around 0.4 probably will have the grain.

[dandelO]

You could also try dropping 'sample jitter', if raising the atmo samples is adding too much time.
Less sample jittering=less randomness in the atmo though, as far as I can work out. A really dense and noise free fog/haze can be created with really low samples if you drop the sample jitter level from the default '1'.

*EDIT: Ignore that. ^^ It only seems to smooth out the atmosphere when there are no rays being cast through it from cloud layers. Doh!

[Tangled-Universe]

You could also try dropping 'sample jitter', if raising the atmo samples is adding too much time.
Less sample jittering=less randomness in the atmo though, as far as I can work out. A really dense and noise free fog/haze can be created with really low samples if you drop the sample jitter level from the default '1'.

*EDIT: Ignore that. ^^ It only seems to smooth out the atmosphere when there are no rays being cast through it from cloud layers. Doh!

If I'm correct reducing sample jitter also reduces rendertime somewhat.
But be careful, reducing it too much can cause visible banding in the sky.

Martin

[dandelO]

It really reduces ther graininess by dropping SJ but, if there are rays in shot, they really suffer from band/patching, yes.

0.25 is really as low as I'd drop SJ, normally. And PS doesn't advise it at all.

I'm preparing an example, it's quite cool in itself, I've realised you can make clouds from the haze rays. Edit shortly...

*EDIT:

Here's some cloud-cast rays with an atmosphere sample jitter of '1'...
[attachimg=#]

Here's exactly the same thing, with an atmo SJ level '0'...
[attachimg=#]

[Tangled-Universe]

Cheap clouds!