Remove clouds from a specific area?

[kent_m]

Hi all, I'm looking for a way to remove clouds from a specific part of an 'easy cloud' layer. Basically I want to eliminate clouds from overhead. I recall there is a way to do this but I can't find that way at the moment... a negative cloud? a Boolean?... Any advice appreciated, thanks very much

[Dune]

I would do it like this. White or 1 for total coverage and then a black SSS for located no cloud, whether hard, soft, circular, square, warped or whatever. Set SSS to final position for a fixed location, if you want to move the clouds.

[kent_m]

Hey there, thanks for your reply.

I've found the SSS but I'm not understanding what the "white" is or how to create it. Can you explain a bit further?

EDIT: Ah, I think I got it - Constant Color

[kent_m]

this appears to be giving a pretty hard edge end to the clouds, almost like  an 'eye of the hurricane' effect. I'm looking for something in this case a bit more natural, like the louds just didn't generate overheard, but are naturally filled out away from the center.

Do you know if there's a way to use a cloud as a sort of boolean cutter to a base layer of clouds?

[Dune]

You get set the softness of the edge (which I didn't), even go above 100%, like 150 or 200 may help. You can also take that mask through a surface shader to give the 'grey' soft masking edge some detail. Mask a surface shader by that SSS (and the 1 or white constant), set its color to white, work on the breakup to make a cloudlike breakup (not so much warp, no distortion, different sizes). The grey gradient will thus be broken up cloudlike.
You could probably also make another cloud seed, and if you have a cloud that would nicely act as an excluding mask, multiply inversely. That would be another way.
Or use a Photoshop painted image map...

[kent_m]

Thanks again for your help