PDA

View Full Version : Realflow foam?


cgbeige
07-30-2009, 10:53 PM
I see all these scripts around to generate foam for Realflow but no one talks about the best techniques for rendering it. any ideas as to what's the best scheme to get something like this surface foam:

http://www.alexanderslatter.com/images/hires/Wave-Foam-Study.jpg

or this falling foam:

http://seandavey.com/wordpress/wp-content/uploads/kieren_3-3.jpg

ytsejam1976
07-30-2009, 11:07 PM
oh yeah. Intersting thread. I have the same question, but for boat particles foam to render.

Cheesestraws
07-30-2009, 11:16 PM
See Vikas's posts in this (http://forums.cgsociety.org/showthread.php?f=86&t=721332&page=6&pp=15&highlight=waterfall) thread, basically lots of cloud particles.

cgbeige
07-30-2009, 11:42 PM
ok - I'll check that out. thanks

cgbeige
07-31-2009, 12:24 AM
I'm getting some nice results already just with a cloud particle mapped onto the imported Realflow particles but how do I get self-shadowing and lighting? I'm kind of a newb with software particles.

ytsejam1976
07-31-2009, 12:37 AM
cgbeige. I don't have very good results, but one question, you simulate in unit scale?. Because i have a boat that is in scale and the simuation from realflow is ok, maybe little more particles, but not the problem. I see that in waterfall of viki, the radius is small, but the waterfall have a good result. But in my simulation if i set my radius as viki waterfall, i have only little point and not good water foam.

ytsejam1976
07-31-2009, 12:44 AM
[URL=http://img389.imageshack.us/i/98533085. (http://img389.imageshack.us/i/98533085.jpg/)

[URL=http://img207.imageshack.us/i/77399571 (http://img207.imageshack.us/i/77399571.jpg/)


First image point. Second clouds with original settting of waterfall

cgbeige
07-31-2009, 07:18 AM
try more particles (you're not getting much definition in the wake so in Realflow, up the density but make sure to up the resolution as well since changing the density will make your particles heavier) and use a less white cloud particle. maybe someone else can help you get more control over the lifespan definition since it's very uniform. I'm not very good with particles but my guess would be to fade them more as they fall.

I'm lucky - I only need this to look good for a single print frame. I might just sculpt the wave and then use the texture2Particles script to make the foam particles and throw in some Realflow meshes for the droplets.

Cheesestraws
07-31-2009, 08:48 AM
Cloud particles only seem to self-shadow when you use ray-traced shadows under mental ray.

I don't have Maya with me right now but I guess cloud type particles radius is measured in world space, which would explain why you can't just use the same settings ytsejam1976. You probably are going to want to introduce a little colour randomisation on your particles and vary the colour over their age. Shadowing should help bring more definition too.

cgbeige
07-31-2009, 04:38 PM
so I've done two tests. The first is for surface foam, which is just a texture converted to particles on top of a nurbs plane with a script from highend3d (it's very slow if you want anything in the area of 300,000 particles, go for a walk):

http://www.3eige.com/ars/particlesontest.jpghttp://www.3eige.com/cgtalk/particlesontest.jpg

That doesn't animate so the techniques's not much use to most people here.

I'll post the second in a bit.

Cheesestraws
07-31-2009, 04:55 PM
Why not just texture the emission rate? Give the particles some random velocity in Y and add a volume axis field with some noise and general direction for you wind. If you are emitting lots of particles like that though you will probably want them to have a very short lifespan, which shouldn't be too noticeable if you are emitting lots from a texture.

You could have the particles collide with the plane but that is going to slow things down quite a lot.

cgbeige
07-31-2009, 05:01 PM
that's a good idea. like I said, I'm a newb when it comes to particles so I'm likely doing half this stuff ass-backwards. If I use a 2k texture map for the emission, will it slow to a crawl or crash? Also, if I want more particles around the edges, do I just up the values on the greyscale img?

Cheesestraws
07-31-2009, 05:10 PM
Should be fine, yes it scales the emission based on the value. By default it will emit 100% from white and linearly scale down to 0% in black areas, this can be reversed though. Just connect the texture to the texture rate on the emitter and click enable texture rate.

cgbeige
07-31-2009, 05:33 PM
here are the wave foam tests. I'm basically just driving a fast square particle emitter off a cliff, Disney lemmings style so it is too uniform. I'm going to do some randomization next within Realflow.

http://www.3eige.com/cgtalk/waveparticlesscene.43.jpg

http://www.3eige.com/cgtalk/realwavetest3-wavecollideref.jpg

Cheesestraws
07-31-2009, 05:39 PM
When adding randomisation to particles it is a good idea to split any fields adding nosie into separate fields. So have one for low frequency high amplitude noise and one for high frequency low amplitude. I also like to use a drag field with a random magnitude per-particle.

Also try animating the offset values in the general direction of your particle movement.

cgbeige
07-31-2009, 06:13 PM
cool - thx. The last part might be overkill though since this is for a still image.

CGTalk Moderation
07-31-2009, 06:13 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.