Forums Technical Discussion Velocity field to advect particle fluid sim?

Velocity field to advect particle fluid sim?

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stevenong
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Hi,

Has anyone tried to use a velocity field to advect a particle fluid sim or points in general?

I'm trying to set this up to no avail. I've attached a simple setup of my failed attempt.

Thanks!

Cheers!
steven

Attachments:
velfield_advect_test.hip (140.4 KB)

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anakin78z
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I tried a slightly different approach, using 3 volume primitives as a vector field using the Sop Vector Field dop, and plugging that into the second input of the fieldforce1 dop. This seems to work, except that you have to crank the foces way up in the fieldforce dop (I went over 1000).

-z
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stevenong
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Hey dude,

I got it to work with a sopgeo reading in the velocity field and will upload an updated hip file tomorrow.

I would like to see a hip file of your setup though so please upload if you can.

Thanks!

Cheers!
steven
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BradHerman
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What sop did you end up using to bring the fluid data in?
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jason_iversen
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The FileSOP in H9.1 can directly read .sim files- a great thing indeed.
Jason Iversen, Technology Supervisor & FX Pipeline/R+D Lead @ Weta FX
also, http://www.odforce.net [www.odforce.net]
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probbins
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Here's a nice simple setup, the key being the need for volumes to generate the vector fields.

Attachments:
particle_fluid_advect_PR.hip (132.3 KB)

“gravity is not a force, it is a boundary layer”
“everything is coincident”
“Love; the state of suspended anticipation.”
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probbins
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A clarification on the file I submitted, there's a filedata dop in there; it's not needed really. I just forgot to take it out.


I have a question as well. The gas advect doesn't seem to add a noticeable amount of computational time. Why would that be?
“gravity is not a force, it is a boundary layer”
“everything is coincident”
“Love; the state of suspended anticipation.”
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jacob clark
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Is there a way to get the velocity field directly into the particles velocity, as opposed to using it as a force?
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hoknamahn
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Hey Jacob,
Bake out velocity field and do volumesample() in POPs. Easy and simple… In this way you can control amount of sampled velocity, you can mix it with DFN and so on.
f = conserve . diffuse . advect . add

fx td @ the mill
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BradHerman
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I ended up useing the FileSOP with vel in the atribs and thevolumesample expression (thanks Jason) on a point sop that was a grid in order to get fast access to the data. Worked out very well.
Thanks for the help everyone.
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jacob clark
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I am curious though… is it possible to keep the setup in DOPs? It seems limiting to be able to control points in DOPs with forces only? Then again, I still have much to play w/ on the POP solver, I'm sure that would give the way forward.
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stevenong
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Hey Jacob,

You can keep it in DOPs but you'll be running a fluid sim to advect your particles at the same time. Check out the Embed in Fluid tool under the Fluids shelf.

Cheers!
steven
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