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nerubz
10-29-2007, 01:30 PM
This is a shot of the asteroid from the "Armageddon" movie.
http://img526.imageshack.us/img526/873/bscap000am9.th.jpg (http://img526.imageshack.us/my.php?image=bscap000am9.jpg)

I was trying really hard to achieve the effect of that greenish smoke/dust/whatever it is, but it just wouldn't work. This is what I came up so far: http://www.vbox7.com/play:999fc6c2

feldy
10-29-2007, 08:30 PM
it looks like your on to the right track. it looks likes theres a bit to much turblulance . other then that your gunna need a ton more layers. take a look at this thread http://forums.cgsociety.org/showthread.php?f=206&t=445722&page=1&pp=15 its about a render that looks like its right up your alley for this shot.

as for colors and so on you can do a lot of that in post if that suits you. other then that Brandon Davis hangs around here from time to time he worked on the movie itself and should be able to give you a better answer on how they did that shot.

nerubz
10-29-2007, 08:40 PM
iother then that Brandon Davis hangs around here from time to time he worked on the movie itself and should be able to give you a better answer on how they did that shot.

I totally lost it when I read that. And I'm gonna lose it one more time if I hear a word about that effect from Brandon Davis you know :)

Anyway, I will check that thread that you suggested, thanks.

feldy
10-29-2007, 08:45 PM
I totally lost it when I read that. And I'm gonna lose it one more time if I hear a word about that effect from Brandon Davis you know :)

Anyway, I will check that thread that you suggested, thanks.


what do you mean by lost it. as you lost understanding of what i was telling you?

nerubz
10-29-2007, 08:49 PM
nope, with "lost it" I meant "lost control" or "freaked out"... nevermind :)

feldy
10-29-2007, 08:53 PM
you thought it would be easy :)

BrandonD
10-29-2007, 11:49 PM
Ha! That effect was done with Jim Hourihan's in-house Hookah fluid-ish software at Dreamquest about 10 years ago. It's very similar to what you could do now with FumeFX & Krakatoa, but wouldn't take two weeks to process and be much easier to setup. The main thing you need to work on, as mentioned, is the turbulence. You'll want to emit streams from lots of points on the mesh, then slowly ramp in some low frequency turbulence as well as some detailed high frequency as well (that's pretty much a common methodology). As for rendering, that's where it'll get interesting. A point renderer like Krakatoa will give you the closest to what was processed via Hookah. Otherwise you'll need to render lots and lots and lots of little ShapeFacing particles. I mentioned FumeFX because you could create a velocity field to advect particles through to get more realistic turbulence, but it's not 100% necessary.

nerubz
10-30-2007, 12:27 AM
Thanks alot Brandon! It feels so good to hear an advice from the actual guy who actually worked on that great movie!

Back to the topic now, I was told some time ago what Krakatoa can do, and I decided to get my hands on the trial version. Anyway, you are suggesting to have two or more wind forces with different turbulences if I got you right, and also to emit particles from more points on the asteroid. Looks like I'm gonna have to experiment alot, so I better get working :) You can check my progress in the Animation WIP section if you like (as well as anyone else ofcourse).

Cheers!

BrandonD
10-30-2007, 01:15 AM
PositionObject > selected verts That's a way to emit from specific user-defined points on the emitter mesh. You could also do the less controlable "Specific Points."

As for turbulence, yes two different scale Wind SWs works pretty well. Start with a large one (values depend on scene scale) with Strength 0.1, Freq 0.1, and Scale 0.01 and adjust from there. The higher the Scale number, the smaller the detail of the noise (generally). Also the noise field is locked to the icon, so animate it moving through one axis (preferably the direction of travel) to add a 4d component to the look. Then do the same, but with a smaller scale noise and adjust their strengths to add the right amount of turbulence to the effect.

nerubz
10-30-2007, 10:26 AM
Yep, it started looking like what I wanted. Can I ask you how many particles you had for the asteroid in Armageddon?

Thanks again :)

BrandonD
10-30-2007, 04:48 PM
I didn't do that effect, but from what I remember Hookah was designed to process millions of particles. This exactly why I mentioned Krakatoa because it renders particles similiarly as points and not geometry. You can still get a similar look with lots and lots of facing particles set very small, something we couldn't do ten years ago on our dual PPro 200s with 256mb RAM ;)

So to reiterate, if I wanted to match the look of the colored gasses streaming off the asteroid I'd use FumeFX to create a velocity field that I'd advect several PF Sources through, then render with Krakatoa. That would generally match the methodology, but you could get half-way there without plugins still.

feldy
10-31-2007, 02:00 AM
Dreamquest..... I sit with a guy who worked there in the 2d department before this shot was done.

Bobo
10-31-2007, 04:00 AM
Yep, it started looking like what I wanted. Can I ask you how many particles you had for the asteroid in Armageddon?

Thanks again :)

While I don't know how many particles were used on the shot, I would like to mention that the main mistake most new users make when starting with Krakatoa is setting the global density too high. The best approach is to keep the density very low (around 0.005 which in the UI is expressed as 5.0 / -3) and then crank up the count. Another common mistake is overdoing the quantities - just because you can render 50 or 100 million particles does not mean you have to ;) When you keep the density settings constant and increase the number of particles, Krakatoa tries to compensate for the changing density, so the final result should look more refined, but about as dense. So a good workflow is to create 100K or 1M particles, find the right density settings, then either increase the count or generate about 10 partitions and render 10M or whatever count is needed to get a smooth effect.

So as a rule of thumb - if you can SEE a single particle outside of the cloud with naked eye in the VFB, your density is too high...

muzbee3d
10-31-2007, 04:34 AM
TRY the particle rendering effect plug-in KY_Trail.
Set it to shorter trail duration and turn the trail noise tool way up !
Tweek trail decay and size.
Effect your with particles forces to waft them around.

oatz
10-31-2007, 03:24 PM
I'd use FumeFX
Is there any trial version for FumeFX? I'm interested in trying it out.

BrandonD
10-31-2007, 04:51 PM
I don't think there's a demo available yet, but if you can find a way to fit it into the budget of one of your projects, seriously consider doing so. Of all the fluid systems I've used (Maya, Houdini, MAX, proprietary) it's the best combination of ease of use, speed and overall quality. One of my favorite features is the particle integration where you can create a velocity field and advect particles through it. This allows you to add a level of fluid motion to particles without being restricted to a full blown fluid sim.

Combined with Krakatoa, it adds a substantial capability to a MAX effects artist.

nerubz
10-31-2007, 05:11 PM
This turned out to a very useful thread, thanks for all your advices! I've been playing around trying to adjust the two wind SWs' turbulences but seems like I'm starting to lose the clue of what 'turbulence' and 'frequency' are doing, though I thought I had known that. On the other hand, I got a quite crystal explanation of the 'scale' value from BrandonD, for what I say thanks :)

Now back to the 'turbulence' and 'frequency' values. Is the turbulence represented like a wave in the physics meaning of that word? I pretty much remember that a wave has frequency and an amplitude, so what's the third value that's in MAX... oh I got confused again. Help me understand this please :)

Bobo
10-31-2007, 05:59 PM
Now back to the 'turbulence' and 'frequency' values. Is the turbulence represented like a wave in the physics meaning of that word? I pretty much remember that a wave has frequency and an amplitude, so what's the third value that's in MAX... oh I got confused again. Help me understand this please :)

Check out this thread and some of the tools/rigs posted there:
http://forums.cgsociety.org/showthread.php?f=206&t=539405

BrandonD
10-31-2007, 08:11 PM
It's convoluted and a very poorly implemented noise system. Turbulence I think of as noise Amplitude and Frequency is sort of a weird mix of Levels and Amplitude.

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