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everlite
01-31-2007, 06:11 PM
Hey guys,

I'm trying with little success to produce a nice low level myst effect and this got me thinking about atmospheric particle effects in general, and more so how are they're rendered?

Taking a look at the pebl commercial by Digital Domain there's a few good examples of mist in action. http://www.digitaldomain.com/links/comm/behindscenes/BHS1/bhs1.htm

I want to do this without any third party plugins, just Max.

So what's the general process, do you create billboards at varible sizes or just literally render out thousands of particles?

In my own project i've got a scene with buildings/skyscrapers and i want the mist to push through the streets. The trouble with billboards is when they intersect with the geometry you end up with intersection lines, so that don't look too good. So what other options do i have left?

I'd be very happy to hear your thoughts, any tips or suggestions on the subject that you might have.

Cheers - Dave.

charleyc
01-31-2007, 09:03 PM
Use LOTS of smaller facing particles, basically max out your machine with them. You will probably have to render multiple passes to get the density you want, but that is the most straight forward way I can think of to approach this.

mackdadd
02-01-2007, 01:33 AM
I've been chasing realistic smoke and mist for a while in Max, too.
One of the early tutorials I found that helped alot was this one:

http://www.the3dstudio.com/product_details.aspx?id_product=2600

the basic technique here is the movement of the particles, and to make tons of them.
Something I've done to help this along is to make the particles tiny spheres, render them as their own pass, and blur them slightly in compositing.

Another technique I learned from Allan McKay's great particle work is to apply image motion blur to your particles, but in the render panel turn up the image motion blur to an unrealistic amount, so the particles smudge together.

here's some examples of mine where I was happy with the particle stuff.

http://www.mackdadd.com/CG/hand_fire_03-6.mov
http://www.mackdadd.com/D&D/kate_vanish_06_final.mov

Also be sure and check out Pete Draper's education section on his website, and Allan McKay's great tutorials. If you're striving for realism in Max, they are among the best stuff on the web for learning from.

everlite
02-01-2007, 01:53 AM
Cheers, though i'm still having little luck, i'm getting results, but they still look a little CG looking. Though i never thought about blurring them, i guess you could even apply a slight grain in post. I'll post my results tomorrow and see what i come up with.

Nice clips, i've seen the girl one a few times, though i think the particles is a little too subtle, maybe because of the sunlight.

How did you do the flames?

Hey i noticed in the D&D clip above that the plumes of smoke are in RGB, anyone know why / what this pass is used for?

Cheers - Dave.

PiXeL_MoNKeY
02-01-2007, 03:33 AM
The RGB color is used for post relighting and coloring. The colors refer to different lights and by color correcting them you can get different colors and lighting combos. That way you can do realtime relighting in post.
I did the pyroclastic cloud at D2 for this spot, I used rgb lights to render the voxels (with D2's storm) so that the lighting could be controlled interactively in the composite. -Eric

everlite
02-01-2007, 03:58 AM
Cheers Eric,

Is this a general technique or one just used by D&D, if it's general can you suggest any links where i can learn more about this?

Cheers again - Dave.

mackdadd
02-01-2007, 11:14 PM
it's a pretty general technique used most places.
Zach over at SimplyCG did a tutorial using Maya and AE to show it.

http://www.simplycg.net/viewtopic.php?t=2126

oh, and the flames are based off an Allan McKay tutorial that I modifed a bit. His worked great for something sitting there burning, but needed alot of modifying to enable the burning object to shake around. I think it's at his site. it's basically transparent sphere particles overlapping with an additive calculation and the image motion blur cranked unrealistically.

charleyc
02-02-2007, 12:46 AM
oh, and the flames are based off an Allan McKay tutorial that I modifed a bit. His worked great for something sitting there burning, but needed alot of modifying to enable the burning object to shake around. I think it's at his site. it's basically transparent sphere particles overlapping with an additive calculation and the image motion blur cranked unrealistically.

Actually if you just add more particles, they work pretty well for moving objects. They are no where near the fluid sims we have these days, but they make great cheap fire.
www.charleycarlat.com/gallery/movies/Fire.avi (http://www.charleycarlat.com/gallery/movies/Fire.avi)

Here is a quick Mist example. It is 250,000 particles. I blurred them a bit in post to loose the graininess.
www.charleycarlat.com/gallery/movies/PF_Mist.mov (http://www.charleycarlat.com/gallery/movies/PF_Mist.mov)

everlite
02-02-2007, 01:35 AM
Hey thanks for the link, i'll check out the tutorial.

Must say i was fooled for a second there i thought you'd just linked over to the fumefx video sample. Nice lighting.

Cheers again - Dave

mackdadd
02-02-2007, 02:16 AM
wow, charley, good stuff! in fact, now i'm all inspired to go home and try and mimic Fume with PFlow! really cool! what kinda spacewarps do you have on it, just some turbulence and drag?

Gravey
02-02-2007, 05:35 AM
hey charleyc that fire is pretty cool. i like the way the shadows and lighting work. can you share how you did it. like, where the lights are positioned etc to get that effect

charleyc
02-02-2007, 05:37 PM
Must say i was fooled for a second there i thought you'd just linked over to the fumefx video sample. Nice lighting.

Only a very brief second though :)

Thanks for the comments

The mist is basically just a dump of particles on to a bunch of deflectors. There is a slight turbulence from Wind and a 10 unit Drag. When the particles hit the text they move to an event where they are pushed slightly away from the text using Speed by Surface so they don't flatten out. That is the basics. However, to add a bit more subtle airy effect, I use Box3 to let the particle Speed output a Script that is the influence of the Wind turbulence, this can very easily be done using a Script Operator as well. With that, the faster they travel, the more the Force effects them. It is subtle here, but a nice effect to use in general.

I did that fire scene several years ago, I cannot remember now exactly how I did the lighting, but it was one of two ways. Either an omni light in the teapot or several omni's placed around and linked to the teapot (like a small sphere). For some reason I seem to remember using multiple lights (3-6 or so I think) Their intensity is pretty low so that you don't get too noticeable of spots on the ground when they roll though it They are projecting an animated Noise map to give them a flickering color.

charleyc
02-02-2007, 05:47 PM
After watching the fire vid again, I am certain that it is a small sphere of omni's, that is how the teapot casts shadows.

Harvey
02-13-2007, 06:23 AM
Just thought I would offer a quick bit of advice on optimizing your scene. A lot of people have mentioned using a whole bunch of smaller facing particles. Strangely enough its often much faster and easier on your system if you use a bunch of small cubes. While its true that you do in fact have 6 times the number of faces with a cube the calcuationi time to make the particle face the camera is more than it takes to draw the extra faces. I used to use this technique all the time to do wispy soft smoke effects and it actually worked quite well.

That said, and I know you said you want to do this without plugins, but I would never use this approach again, and would much sooner shell out the extra $ for a particle plugin, like Fume or if all you need is a renderer Krakatoa. In fact you can actually use Fume and Krakatoa together.

mackdadd
02-13-2007, 06:17 PM
I used to use this technique all the time to do wispy soft smoke effects and it actually worked quite well.

Are you spinning the boxes quickly and turning on motion blur, or adding a blur in 2D? Or are you mapping them with some soft-edged bitmap?
I've seen people here, Steve Green I think, replicate water pretty convincingly using the rotating box technique instead of facing particles. It looked great.

charleyc
02-13-2007, 07:30 PM
I completely agree with Harvey on plugins. This method is far from ideal and in all honesty, I would bid in the cost (at least in part if I thought I would use it agian later on) of FumeFX or such for this type of thing. As for Krakatoa, I think that if you do much of any particle work, this looks like a product to have.

mackdadd- For this test I actually used Spheres. The more particles you use, the less important the shape is for overall smoothness and shading and the more important for optimization (boxes or tetras have less faces). But with Spheres, you can sometimes get a smoother effect with less particles, especially with slow moving particles as you have less motion blur. Spinning boxes work great for water running as you can get a nice sparkle effect.

Harvey
02-15-2007, 09:42 AM
Yes, boxes do work great for water though thats not what I was refering to here. I simply use a very basic material...just a color in the diffuse and the opacity set very low, and for mist no specular at all as mist doesn't typically sparkle. Then when you have a lot of particles they simply add up together to create a soft effect. The boxes should also be very small. Essentially this is replicating a point render inside max without scripting one (which you could do actually). The down side is you need a lot of particles, though as I said boxes are faster than facing particles. Spheres can also work great but again produce a slighly different look. I reccomend experimenting with different shapes, opacity settings and particles counts...you would be surprised with the looks you can achieve with simple objects and materials.

All that said I would definately look at some of the plugins out there as if you are using particles for professional work you can't really go wrong with a plugin that only a few hundred bucks...just build it into the cost. That said here are some essential things to check out:

Krakatoa - rendering
Fume - fluid effects and rendering
Particle Flow Box Sets - an absolute must for getting control over you particles
Thinking Particles - expensive but a fantastic alternative if you want to go with an entirely different system that particle flow.

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