When 3D clouds look grainy...

[kepler]

See the image in attachment: I have used quality setting 0.8 for the rendering, quality 1 for the clouds and 32 samples for the atmosphere, but it still looks very grainy. What do you think should I do to improve that image? It seems strange, but if you look on the top-left corner there are some clouds that seems better-looking.

[Njen]

From looking at the image, I see the grain appear mainly where there are godrays. The fact that, as you mentioned, the clouds look fine in the top left corner is because the sun doesn't shine through the atmosphere between those clouds and the camera (the clouds in the distance are shadowing the clouds in the foreground).

Have you used Ray Tracing in your atmosphere? Either way, it am certain that it is an atmosphere samples issue. Try 64 samples in a cropped render and see if that cleans your image right up.

[Rich]

i dont know for sure but they look pretty thick, you may have to do many more samples. ive used 256 before...

[rcallicotte]

Right.  I've used over 200 samples before for clouds.

[chris.arceo]

What i have found that helps is increasing the atmosphere quality to 50 or higher. I also use a quality of 1.25-2 (depending on how thick the clouds are) on my cloud layers that are close to the camera.

[oggyb]

so my using 51830 samples for my current render is overkill then?    I agree with chris about having atmo at 50 or above.

M.

[Oshyan]

This looks like a simple problem of atmosphere samples since, as others have pointed out, the majority of the noise seems to be in the light rays of the atmosphere. 32 is generally a good value for "final" quality atmospherics but with rays and other complex effects higher levels are often necessary. I would try 64 or even 128 samples in the atmosphere quality tab. Changing cloud samples probably won't help much in the most needed areas.

Turning on raytracing in the atmosphere won't help at all here and is generally discouraged except in scenes where you have shadows from the *terrain* that would be visible in the atmosphere.

- Oshyan

[king_tiger_666]

50000 samples?.... how long do you want a render to take?!!!!

[oggyb]

lol, sometimes big tall clouds just need that I guess, to be really beautiful.  Doesn't matter about time, I can only render small anyway.

M.

[kepler]

Thanks for your replies! I need to experiment a bit with the various parameters...

[hyper1]

Kepler,
There is a way to test your scene to insure that your settings are adequate for no grain.   Try setting your sample rate between 256 and 512.  Render with a cropped region of the most troublesome location (saves lots of time).  If your still getting grain turn off the acceleration cache available under the "quality" tab.  Then be prepaired for very long renders!   Right now TG2 is capable of most atmospheric features, however clouds and reflections are likely to take up the greatest amount of render time (I might add that this is true in Vue 6 as well).  Under certain circumstances, no matter what software you use, it can pay to touch up post. 

Grain shows up most in high contrast situations.

Thanks for your replies! I need to experiment a bit with the various parameters...

[Oshyan]

Turning off the acceleration cache should not affect grain.

50,000 cloud samples is truly insane and should not be attempted in my opinion. Something is seriously wrong if you need to go over 1000, let alone 10,000. 

- Oshyan

[Dark Fire]

so my using 51830 samples for my current render is overkill then?    I agree with chris about having atmo at 50 or above.

M.

Has that render finished yet?

[gradient]

Although the cloud render features of TG2 are a vast improvement over 0.9XX.....I must say that the one area of disappointment has been the graininess.  I am not saying this just now.....if you look at some of my comments made on the alpha renders of last year over at Renderosity...you will see that I made the same statements then.  I have yet to see a decent 3D cloud render that is free of grain/noise....if they are out there...let's see them!