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Posted: Jul 10, 2009
Category: Autodesk Maya, Example scenes, Resources, Tips and Tricks, Tutorials
A few years ago I put together a learning Maya Fluids Dvd with Neehar Karnik. It contained numerous tutorial videos along with mel scripts and scene files. The material is still relevant today, although the Dvd was no longer offered in the Autodesk store.
Now the full contents are available here for free to Maya Subscription customers:
www.autodesk.com/subscription
Once logged in goto: Training/Autodesk Maya/ Training Videos/Dynamics
As well many of the video tutorials are available to all on the Autodesk youtube channel:
http://www.youtube.com/view_play_list?p=A7756842D6CE3BFD
Note that I would today use nParticles instead of the old system for most of the examples, although for the most part it should be trivial to replace any use of particles with nParticles, as nParticles is derived from classic particles.
Here is the original blurb with the Dvd:
Maya Techniques | Maya Fluid Effects is your key to unlocking the power of Maya Fluid Effects. With a special focus on working with expressions, you'll learn how to combine particle system and fluids to produce a wide variety of effects. Learn how to make full use of fluids by writing expressions. Master water related effects such as creating foam on an ocean surface using both particles and fluid. Learn to create the most effective gaseous effects, as well as flames and explosions. Understand how to work with Fluid Textures plus hints on how the Maya Fluid Navier-Stokes solver can be used for crowd simulation and more. Included with this DVD are dozens of scene files, created by the experts, to help you learn as you work.
225 min
You Will Learn:
Oceans
Oceans and the Height Field Node
Fluid and Expression Basics
Water Shading
Water Spray and Foam
Water Wakes
Rivers and Flowing Liquids
Gaseous Effects
Flames and Explosions
Smoke and Clouds
Snow
Simulations
Data Transfer
Special Uses of Fluids
Crowd Simulation
Sound Waves
Fluid Texture Uses
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In order to post any comments, you must be logged in!
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| Posted by Nizan on Jan 12, 2011 at 12:41 PM
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Hi Duncan..
Thanks! I think I should probably post your reply in some forum.. Very informative! :)
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| Posted by Duncan Brinsmead on Jan 10, 2011 at 08:33 PM
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Substeps can affect the simulation in a couple of ways.
- by using smaller time steps the flow can better resolve incompressibility and high velocity flow, which can sometimes dramatically change the simulation by reducing artifacts (Maya fluid is designed to work with large time steps, but instead of blowing up it tends to have excessive diffusion for large steps)
- In some situations small changes to the simulation can have a dramatic effect on outcomes (the butterfly effect)
- emission currently doesn't occur on substeps, which can lead to some differences, although total emitted should stay the same. However emission does occur on subframes when caching with oversampling.
We try to ensure that the behavior of the fluid is roughly the same for different timestep values, but there tends to be a difference because we have a rather large default timestep.(one step per frame) However there may still be some behaviors that are not properly adjusting for the timestep(i.e. bugs)
The quality attribute controls the amount we iterate on the Poisson solve, thus affects the incompressibility of the flow. Low quality values are less different when using the high detail solve method, because it uses the pressure from the previous timestep as a starting value, while the default method always starts from zero pressure.
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| Posted by Nizan on Jan 08, 2011 at 04:50 AM
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Thanks :)
There aren't that many jobs in the academy for high-energy physicists.. You have to be some kind of genius to get one..
What's still confusing me about the simulation engines for the fluids and nparticles is that some physical attributes are controlled by parameters of the solvers, like substeps and quality.. Their affect on the behavior isn't something I could have guessed..
And thanks again!
Nizan.
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| Posted by Duncan Brinsmead on Jan 05, 2011 at 03:00 PM
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The Navier Stokes model is a 2d incompressible flow, not a heightfield water model, and thus will not yield natural looking wakes. Sometimes one can get nice looking results with the ns model for a height field, however. In some cases it can create the look of standing waves in a flowing river, for example. Thus one can get things like the buildup of flow around bridge pylons ). The reynolds number is determined by the viscosity. (we use a formula to convert the viscosity into a reynolds value internally for the ns model, but I don't think you can really calibrate it very easily to water and scene scale. It is best just to play with the values to get a good looking effect, not try to enter emperical values ). Also sometimes when using the ns model for a heightfield it is useful to relax the incompressibility of the flow by lowering the quality attribute. Forward advection may also be useful. One can also get interesting effects by using negative density gradient force. (which is almost like a shallow water model, but very crude)
I think a physics PHD is a great asset when getting work as a TD in simulation or research at one of the larger animation houses that support this kind of work, or in a games or software development company like Autodesk. However getting work in the 3d market( at least in computer animation ) is never easy, and jobs have been a bit tight lately.
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| Posted by Nizan on Jan 05, 2011 at 03:38 AM
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Cool, thanks :)
And another question (let me know if I nag too much). I was trying to use the wake fluid to create "swelling" near an obstacle.. It seems the spring mesh solver gives too-linear results, so I switched to Navier-Stocks.. But I'm having trouble figuring out the scales.. How would I go about calculating the Reynolds number from the flow? Do you happen to know if that swelling is a result of depth-waves hitting the obstacle or just something related to the viscosity/compressibility of the flow?
Btw, do you think it'll be easy for a physics phd to find a job on the 3d market? :)
Thanks,
Nizan.
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