Fake cloud quality - gaussian blur

[PorcupineFloyd]

I was slightly editing my render in Photoshop by adjusting levels and adding some diffuse glow and realized that in some situations it's very useful to select a cloud puff and apply a 1 px gaussian blur to it. However, it works well only if the edited area's background is plan, for example if there is a small cumulus puff with darker and plain background (a small cloud on top of bigger one obscured partially by it's own shadow).

I've found that results are quite impressive. I had most of clouds rendered without noise but those smaller parts, divided from the rest - a bit noisy and by applying simply 1 px gaussian blur - they look almost identical to those without noise.

So my question regarding this technique is pretty straightforward - would it be possible to implement cloud blurring as a part of render process? It would save hours of render time if doing renders in high resolutions because of less samples. The biggest problem however (I think so, as I'm not doing any programming at all) might be blurring clouds while still maintaining sharp detail in the background (transparency).

Is it possible and makes any sense at all?

[rcallicotte]

You can apply noise to your clouds in the Density Shaders of the cloud shaders.

[PorcupineFloyd]

You mean noise octaves?

[Tangled-Universe]

I am not really sure what you mean/want...

You want to render higher resolution with lower sample-levels, ending up with more noise and then have it being blurred by the renderer?
I think with a little practice it is not so difficult to find the right trade-off between noise/quality and the renderspeed.
The density fractal also gives you control about how much puffs you'll end up...
It's all possible already, it takes time to figure out (awful lots of time sometimes lol).

Martin

[rcallicotte]

Nope.  Like in the Density Shader's Tweak Noise and Density settings.  You can create noise in there that will do all kinds of things...not to mention what you can do with the Lighting settings in the Cloud Layer.

[PorcupineFloyd]

Let's say we have a scene with cumulus layer. In order to render it without noise you need to set cloud samples to for example 512, but the same result could be achieved with setting noise samples to for example half of it but with blurring whole clouds with gaussian blur set on 1 pixel radius.

I was thinking about implementing gaussian blur into renderer so TG2 could render clouds, apply slight (1 pixel in radius) blur to them while maintaining detail in the background.

[rcallicotte]

I would play around with the values as much as you can.  The lighting properties on a cloud layer might be a good place for you to start.

[PorcupineFloyd]

Yes, but still - as far as I know there is no setting to simply blur features. I can decrease or increase detail, noise, tweak shape or lightning and what I mean is to simply blur noisy parts of clouds.

[rcallicotte]

I understand.  There is no Blur Function.  But, the other things you mentioned are in essence the same thing.

[PorcupineFloyd]

Yes indeed. But they require lots of time to compute in contrast to applying a blur. That's why I was asking if it is possible to implement cloud blurring in TG.

[rcallicotte]

Right.  Good point. 

Maybe this is something for a to-do list for later, once the product goes Gold, but I don't know much about how that end of it works.

[PorcupineFloyd]

Let's see what the devs will say

[Hetzen]

I could certainly see the use of a Gaussian Blur shader, but it won't help on cloud edges.

I've found a dramatic improvement on my renders by increasing the Atmospheric samples to about 100. I'm only basing this on a specific scene I'm working on, but it has knocked out a hell of a lot of noise.

[Oshyan]

There may be possible value in a "sample blur" setting in some cases, but it would also tend to reduce detail. Something to think about for the future, but it's not going to be added in the near future at the least.

- Oshyan

[PorcupineFloyd]

That's great news Oshyan! I'm quite sure that it could do some good stuff if tweaked properly (as with acceleration cache).

Increasing atmospheric samples is a good way to reduce noise but it also consumes tremendous amounts of time.