Ole Posted May 10, 2011 Share Posted May 10, 2011 Hello Odforce. I am currently trying to wrap my brain around art directing smoke and fluids, and I would like to ask you to help me out with some issues that I am having troubles with understanding. I'm creating an effect where smoke has to travel from a source (nothing fancy) along a path. It has to maintain its volume and still look fluid-like (lots of turbulence). At the end of the path, it has to flow into a deforming recognizable shape. Currently I am able to have the smoke follow the path using a custom velocity field, but I am having issues with the rest. I've read a little about divergence and gradient fields, but don't know where they fit in in my situation. I've also looked at the "smoke path follow" videos on vimeo, but I don't really understand how to make use of the information provided My deadline is quite tight considering the task, so I figured I'd ask you guys before the situation gets really hairy. If you have any insight, files or bookmarks laying around, please do share. Thanks, Ole 1 1 Quote Link to comment Share on other sites More sharing options...
Peter Quint Posted May 11, 2011 Share Posted May 11, 2011 Hello Odforce. I am currently trying to wrap my brain around art directing smoke and fluids, and I would like to ask you to help me out with some issues that I am having troubles with understanding. I'm creating an effect where smoke has to travel from a source (nothing fancy) along a path. It has to maintain its volume and still look fluid-like (lots of turbulence). At the end of the path, it has to flow into a deforming recognizable shape. Currently I am able to have the smoke follow the path using a custom velocity field, but I am having issues with the rest. I've read a little about divergence and gradient fields, but don't know where they fit in in my situation. I've also looked at the "smoke path follow" videos on vimeo, but I don't really understand how to make use of the information provided My deadline is quite tight considering the task, so I figured I'd ask you guys before the situation gets really hairy. If you have any insight, files or bookmarks laying around, please do share. Thanks, Ole Are you talking about this when you mention vimeo videos? http://vimeo.com/11194348 One basic technique is animate a whole bunch of particles, emit smoke from them, make sure the smoke is dissipating really fast. Hope that helps. 1 1 Quote Link to comment Share on other sites More sharing options...
ikarus Posted May 12, 2011 Share Posted May 12, 2011 i think what he means is using tangents to direct motion of fluid and using gradients to constrain the fluid to a space essentially a gradient field is a vector field that "points" towards the surface of a levelset, in fluid fx context it allows you to "push" fluid into a shape thats defined by a sdf, since the gradient field is pointing towards the sdf surface houdini 11 added a few assets for the "Attract Fluid" shelf tool which do exactly this, specifically Gas Target Force, i added a simple example file with tangent velocity fields and the gas target force showing this someone can probably explain this better than me, though fluidconstraint.hip 2 Quote Link to comment Share on other sites More sharing options...
Ole Posted May 13, 2011 Author Share Posted May 13, 2011 Thank you for the replies. Emitting smoke from particles was not an option for several reasons. Mainly because it has to look like the fluid it self is moving and not being emitted along the way, and second because particle emission tends to be very noisy (in my experience). The Attract Fluid tool is what I am using in my current setup also. However, a couple of new issues and revelations appeared. The main issue now is to have the fluid take the shape of the goal object. It is just too much smoke being emitted for it to fit on the smaller object. Unfortunately, the emission amount can not be reduced. I also had issues with the fluid not settling at the goal, but this can be tweaked with Velocity Dampening in the Pyro Solver. Another issue is also the Curve -> empty space -> goal handoff. The transistion between the forced velocity stage and attraction stage is very hard to get right (the smoke mushrooms at the end of the path), so I tried to adapt the velocity setup to be a force instead. In my tests, it didn't work very well because the smoke gets smeared out along the curve and it doesn't follow the curve good enough. So, that's where I stand right now. I am also looking into simulating the whole thing backwards, but am afraid the motion won't be as nice and natural. Quote Link to comment Share on other sites More sharing options...
Pazuzu Posted May 25, 2011 Share Posted May 25, 2011 Hi!!! Here i put the file for the Smoke path follow. http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=22162 1 Quote Link to comment Share on other sites More sharing options...
Ole Posted May 26, 2011 Author Share Posted May 26, 2011 Hi!!! Here i put the file for the Smoke path follow. http://www.sidefx.co...ewtopic&t=22162 Thank you Alejandro! Very generous of you to share the file! Quote Link to comment Share on other sites More sharing options...
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