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Old 09-27-2012, 07:44 AM   #1
Venator11387
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Oil and Steam FX

I am currently creating oil and steam fx. I am not really going for super realistic look, but more of an animated film style. I am using Maya fluids for all of them. I tried out nParticles for oil as well, but the results were not as nice and the "nParticles to polygons" conversion kept giving me problems.

1.) For the Steam FX , near the point of emission in the reference, there is a strong clean stream at the beginning. After the stream, the steam spreads/expands and swirl. The spread/expand part is the trickiest effect of the sim I am trying to get. So far the look seems more like particle clouds rather than a smoother fluid.

Here is the main reference I am using: link

2.) The Bubbling Oil test that is based on this boiling water tutorial:

I am trying to get bubble burst effects similar to the reference. Which particular settings should I focus on to get that effect? As seen in the playblast, part of the trouble is that the polygon spheres I am using as collisions also fill internally with fluid as they rise up. The result is not a natural bubble burst or one that does not allow the bounce to happen.

Bubbling oil reference: link

3.) For the Falling Oil , the main concern for the moment is the way the fluids interacting with the ground, as they are sliding around too much. The only solution I could find right now is viscosity, but that will also change the behavior too much as well. In addition, small bits of the fluid keep disappearing/reappearing.

Last edited by Venator11387 : 09-27-2012 at 08:51 PM.
 
Old 10-02-2012, 12:10 AM   #2
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Duncan Brinsmead
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I've attached a simple fluids scene roughly matching your steam reference. In order to get very fast steam one needs a high speed emission on the emitter, as well as high substeps and emitInSubsteps ON for the fluid. I also used forward advection with a bit of density pressure and a small emitter. The pressure makes the density expand outward where the density is high. Forward advection is needed to handle expanding (or contracting) density, such that the total density doesn't change. As well to better get a more defined and pointed cone shape on the initial expansion I collided a cone with the fluid (a little like having a nozzle ). (hide the cone for proper rendering)

For the auto resize to expand fast enough one should make the boundaries Open and make autoResizeMargin 1 or 2. There is also density dissipation to keep the fluid from expanding too much.

This steam is very thin, so no need for self shadowing. I did add a lot of velocity swirl and noise, as well as high turbulence. Due to the very high flow speed the all the velocities and turbulence values needed to be extremely high.
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File Type: zip highPressureSteam.zip (2.9 KB, 54 views)
 
Old 10-02-2012, 12:15 AM   #3
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Also for the bubbling check out this tutorial. The main trick was to collide the fluid with bubble geometry. Something similar but with more viscosity might work OK for you. Not sure what you mean by he sliding fluid, but perhaps you want to increase the friction value on the fluid. Also perhaps a tiny bit of damp might help.

http://area.autodesk.com/blogs/duncan/boiling_water

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Old 10-02-2012, 10:09 PM   #4
Venator11387
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Thanks for the replies in this and the other thread Duncan much appreciated! The steam scene has been very helpful!

I actually based my bubbling oil fx off your boiling water tutorial. The thing about the spheres colliding with the fluid is that the inside of the spheres fill up with fluid as it they are moving through. The result is it does not have quite the natural pop effect that happens when a cavity of air reaches a liquid surface. I am wondering if you came across that problem?

I am also new with the liquid aspect of maya fluids. A weird behavior I am coming across constantly is the sudden appearing, disappearing, and even reappearing of particles of the fluid. Those particles may even have different behavior than the main fluid, such as falling very slow or stopping even when they are in the middle of the container. I attached a scene of an oil spray test that I have been attempting (that I will likely start over).

Oil Reference (skip to 5:00 on video)
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File Type: zip Oil_FluidPipeSpray.zip (10.5 KB, 11 views)
 
Old 10-02-2012, 11:10 PM   #5
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The spheres should not fill with fluid providing they start OUTSIDE the fluid( i.e. enter from the bottom ). It might be hard to get a good pop though. It requires very high resolution on the grid to represent a thin bubble.

The liquid feature on the fluid does not at any point create particles... the solution is entirely a volume. There can be problems with creep of density across the volume grid where the density then exceeds the meshing threshold and one gets drops. The small densities are a bit like mist, but it is a balancing act to threshold the water surface at a good point that avoids these densities.
 
Old 10-03-2012, 08:49 AM   #6
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Quote:
The spheres should not fill with fluid providing they start OUTSIDE the fluid( i.e. enter from the bottom )
Actually, I did have the spheres start below and outside the fluid like the instructions in your tutorial, but it still had the same filling up. I thought the geoconnector could help, but to no avail.

I took a shot at your steam method from scratch. The main thing I am trying to get is the expanding effect like you have. In addition, the fluid tends to roll and circulate right at the opening of the cone.
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File Type: zip SteamTest.zip (11.6 KB, 13 views)
 
Old 10-03-2012, 08:49 AM   #7
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