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steering large billowy smoke

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Hey guys, I have a large billowing smoke sim a wall of smoke from different sources. I need to steer the volume, like have it turn at a certain point. What is the best approach to steering or having thick volumes follow a vector. Right now I've tried guiding the smoke using pumps by making some geo that acts as a wall with custom velocity vectors to push to smoke around. It sort of works but the smoke expands a bit too much and doesn't really seem like its being directed, also seems to lose it's volume. any tips would be appreciated

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You could deform the volume post sim, or if you're using pumps, limit the speed of the vel force instead off using add, or try your vel force in advect instead of vel update.

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thanks Christian, I'm seriously considering a lattice on the volume, but I need collisions and it's a [retty foreground element. I actually set up some ramps for controlling the velocity in different parts of the curve and I've been tweaking to get the right amount of vel to push the smoke when it gets to a certain area, it's just super inefficient and not really holding up well. The source volume for the pump is set to add velocity right now, do you reccomend a different operation? I'll try swithcing the pump to go into the advect output of the solver.

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Hey Ryan, 

   I commonly due this to my fluids and smokes. I love to use a curve as a my steering path, I commonly will create a curve, poly wire it and then give it a velocity along the surface and then I create a volume out of that and use that velocity to 'drive' the sim in a direction I like you get a bit more control and! Do I have an example file for you! I saw this a awhile back and its a great technique for control sims!

 

Check out this link and use the file at the top!

http://forums.odforce.net/topic/17056-tornado/?hl=tornado

 

I hope this is not what you tried but I have a picture in my head of what you did so i hope its correct!

 

Cheers!

 

Andrew

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hey thanks Andrew! this is a good idea, is this from the cmi vfx network relationship video? I completely forgot about it. I don;t usually set my source vols to copy because the motion usually doesnt look good it's like i need to add back in another source velocity and mix to get it to look interesting.

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It may be, I did watch the one yet! Thats usually what I end up doing is mixing in (multiplying) the source vel back into the guided vel. I believe one I used the guide velocity as a force which gave it a more natural feel but i would have to check! Post a file when you have something cool! I will be interested to see what you got!

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I'm not sure if it's the best thing to copy velocities into the sim as you won't get much secondary motion.

I came up with a method of getting smoke to follow fields perfectly (or as much as you want).

Basic idea is to add in the velocity, let it go through the solver, then at post_solve remove the velocity, store the result as old_vel and then in pre-solve (next frame) replace vel with old_vel. That way you can tell it to inherit 0.05 of the velocity etc and maintain some of the secondary motion.

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this sounds awesome christian, I'll see if I can get something like that going. If you have an example I would, and I'm sure a lot of other people would greatly appreciate it  :)

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I have a proof of concept scene at work I can post on Monday.

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wow pretty awesome stuff. I like the way you set this up! thanks!!

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