Cumulus layer addin random noise ???

Started by elscorpio, March 22, 2010, 03:41:17 PM

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elscorpio

Hi

i'm trying to get more control over the the clouds layer. So i have used a power fractal as blending shader to the density shader.

and it looks fine looking at the blending shader and the density shader, but on the cumulus layer there seems to be a lot of noise which i want to go away.

I have tried using a color adjust shader and clamping on the black and increasing the black limit but it doesn't remove the noise.

Where is this noise coming from ?

How can i remove it ?

Hope someone can help. Thanks   :)

Regards

Elscorpio

Tangled-Universe

It's likely that the noise is coming from the fractal's "roughness" setting. Decreasing that value might work as well.

elscorpio

Thanks for the reply

The Blending shader's (power fractal) roughness is 0

the density fractals roughness is 1.25

If it's coming from the density fractal then why isn't it appearing in the density fractal preview

also the cumulus layer's Coverage is -0.3

Basicly what i am expecting is for the cumulus layer to be more controlled by the powerfractal and the density fractal. So that clouds would only appear where the power fractal is NOT black. and the the density fractal would only work within the areas specified by the powerfractal. This is all to gain more control over where the clouds are and also how they look internally via the density fractal.

maybe i misunderstand the workings of terragen, maybe it should be set up in another way.  ???


Tangled-Universe

Quote from: elscorpio on March 22, 2010, 05:24:11 PM
Thanks for the reply

The Blending shader's (power fractal) roughness is 0

the density fractals roughness is 1.25

If it's coming from the density fractal then why isn't it appearing in the density fractal preview

also the cumulus layer's Coverage is -0.3

Basicly what i am expecting is for the cumulus layer to be more controlled by the powerfractal and the density fractal. So that clouds would only appear where the power fractal is NOT black. and the the density fractal would only work within the areas specified by the powerfractal. This is all to gain more control over where the clouds are and also how they look internally via the density fractal.

maybe i misunderstand the workings of terragen, maybe it should be set up in another way.  ???



The blending shader's fractal roughness can affect the apearance of your clouds, but since you've set it to 0 that shouldn't be the case, unless you're using scales similar or smaller to the density fractal you want to use for your cloud. I recommend to use quite bigger scales for your blend shader compared to the density fractal.

By default there isn't very much contrast in a powerfractal. So if you set roughness to 0 and keep contrast at ~1 then you might not get the result you expect because the powerfractal's colors are not "bright" enough. If you increase the contrast to around 4 for example then you'll see that the coverage increases a lot and more accordingly to your blending powerfractal.

Clouds are very complex to control precisely. Besides roughness other factors can play a role. For example, high contrast values still can cause noise, but also high edge sharpness or density values in the cloud node can emphasize small scales in the density fractal. A color unclamped colour adjust with black point to ~0.1 and gamma reduced to <0.5 may also aid in reducing roughness.
The tough deal about clouds is to find an ideal situation.

You said the cumulus coverage is -0.3? Or the color offset in the density fractal is -0.3?

Martin

elscorpio

Fantastic !  :D

QuoteBy default there isn't very much contrast in a powerfractal. So if you set roughness to 0 and keep contrast at ~1 then you might not get the result you expect because the powerfractal's colors are not "bright" enough. If you increase the contrast to around 4 for example then you'll see that the coverage increases a lot and more accordingly to your blending powerfractal.

Above advice is what did the job, i played arround with the contrast in the power fractal (blending) shader and now the cumulus layer looks much more like the power fractal.

QuoteA color unclamped colour adjust with black point to ~0.1 and gamma reduced to <0.5 may also aid in reducing roughness.

This had a small effect on noise

There still is some noise, but at least I now know in which direction to go now.

QuoteYou said the cumulus coverage is -0.3? Or the color offset in the density fractal is -0.3?

I changed the cumulus coverage and the power fractal's color offset now, to fit the new settings.

I found that i can control the clumping amount within the cloud by changing the lead-in scale of the density shader  :)

Any way, thank you for your advice, it was really helpful  :)






Tangled-Universe

I'm glad I could have been of any help, you're welcome :)

I was wondering about what you said here:
Quote
I found that i can control the clumping amount within the cloud by changing the lead-in scale of the density shader  :)

How did that work for you? Decreasing it gives more clumps/noise or the other way around?

Cheers,
Martin

elscorpio

oh he he

QuoteHow did that work for you? Decreasing it gives more clumps/noise or the other way around?

it was a diffenrent matter i was talking about, sorry for changing the subject. I just wanted to share some information in case someone else stumbles across this post  :-\

I was just playing arround with the Lead-in scale in the density fractal and this only works within the areas defined by the power fractal. Exactly how i want it  ;D

I have included 2 pictures to show the difference it makes when using high and low lead-in scale, i have zoomed in on the feature that the camera's where looking at from the previous pictures. one picture is with lead scale set to 6000 and the other the lead-in is set to 38000. I also increased the contrast in the density shader to make it more easy to see.
You probably allready knew this....

Any way i will continue to play arround with it and if i find any revelations i will be sure to post them  ;)