Blowing Dust, mist Et cetera

[TheBadger]

Hello,

I am having difficulty making clouds appear as dust or mist, mostly with dust though. Its easy enough to get clouds close to the ground. But making the clouds look like dust particles, is it even possible? http://lasp.colorado.edu/education/outerplanets/images_spacejunk/thumbs/dust.jpg and http://www.lpl.arizona.edu/~abramovo/SpaceShipOne_launch/154-5442_IMG.jpg for something like this http://www.nrcd.org/aguafria/dust.jpg Any ideas?

Also, when animating clouds I understand how to make them change over time, just set a key frame with one seed at one place in time, and another keyframe and seed ant another place and time (Is this correct and the best way?). But if you want the clouds to move across the screen, then what? Just set a key frame for one position and then drag the axis arrows to a new point and set a keyframe? Is that correct and the best method?

Also, I have been trying to make mist by finding a seed of clouds thats fills the image, lowering to the ground, and then trying to 'thin' the clouds. Perhaps there is a better way?

Thank you

[rcallicotte]

I've done dust, so I know it's possible.  So have others.  Just keep tweaking and / or look for examples here and there in these forums.

[Tangled-Universe]

The examples you showed are pretty different. Especially in the latter it is indeed dust being blown in the air by the machines, but the shapes are more like clouds. These require higher density and edge sharpness values compared to settings for mist.

So let's say you want more like low mist. Usually the default settings are good starters for this. Density 0.006 is perhaps a bit high, but good enough for positioning and tweaking your cloud. Eventually you probably need to lower it.

Lowering the cloud to ground level and decreasing depth is definitely the right way. Especially because the thinner the cloud the faster it will render, although that also depends on the density of course. These two values determine the amount of samples needed for rendering the most.
What works excellent is using a constant colour @ 1 as cloud density shader. Then lower the cloud to ground level and adjust depth to your liking.
From there you have 100% coverage (because of the constant colour) so it's very easy to determine the density and edge sharpness you're looking for.
Use a bright sphere or something to asses density of the layer.
After tweaking is done, plug the cloud fractal shader into the cloud node and get rid of the constant colour.

You can indeed move the cloud by changing X or Z values for position and keyframe those. Be aware that nowadays TG2 automatically creates an ease-in and ease-out effect at the beginning and start of the animation.
For a constant movement you can use a "get frame number" function which feeds into a displacement shader, then into a redirect on the axis you would like to move the cloud on. Then feed that into a warp shaders' warp input and put the cloud density fractal in the shader input of the warp fractal.
I think this is how it looks straight from my head/heart.
What it will do is displace/move the cloud with 1m/frame. Logically you can add a multiply scalar operator after the "get frame number" to speed up or slow down the movement.

I would never animate cloud seed by the way, because then with every frame the cloud coverage changes completely.
Unless you're interested in psychedelic stroboscopic animations

Hope this gives you some clues/ideas.

Cheers,
Martin

[rcallicotte]

Not sure how much control you would have with this - http://forums.planetside.co.uk/index.php?action=dlattach;topic=3691.0;attach=12807, but DandelO worked out a pretty controllable cloud that might be useful.

[Tangled-Universe]

I don't think a spherical meta-cloud is very useful, honestly.

[dandelO]

I agree, I don't think that technique really even applies much in TG at all, these days, what with the localise/move options that are now available. Of course, there are still situations where I'd use a 'metacloud' object in such a way as I did before but, not for what I designed it for back then, and certainly not for 'dust'.

TU's advice is good, and also, for a more particle-like effect, this would be one of the situations where I might suggest you'd get nicer/more applicable results by lowering cloud quality significantly. We all know the old story of; 'Raise samples/quality in your cloud layer to remove the grain...' but, if you actually want a grainy effect, do the opposite.

[rcallicotte]

To be clearly honest, I wouldn't use TG2 by itself to create an animated dust storm.  There are too many other products out there.  Blender, for one.

[TheBadger]

OK! So Im getting good looking dust, but im sure there is room for improvement.

Tangled-Universe, I did most of what you described. I didn't use constant colour because I was getting lucky with seeds with just a few clicks. But I will use this method in the future, so thank you. Also, Im pretty perplexed with animation for clouds now, but I'm sure it can be worked through.

I found that working in layers is a good way to go. I set up my main clouds for dust and did as was described above. I then copied the cloud node and shader and checked localize, moving the new cloud layer close to the camera and thinning them by more than half. I also lowered the quality on the second layer as dandelO suggested, for the reason he stated and to add difference.

After I animate the clouds I will add pre-keyed blowing dust for fine detail in front of the camera. Though first I have to animate the clouds successfully

Here is a little render of the progress so far, if you have more thoughts on this please share.