flip fluid vorticity

[R_cyph]

hey all,

I've got a basic flip fluid sim and I want to calculate voritcity and apply it to the particles so I can save it out to disk to bring into 3ds max for rendering.

I've read using the gas analysis node set to curl will give me vorticity, then use the gas field to particle node to apply to the particles but I have no idea how to get these nodes to work. If I open the flip fluid solver node I get msgs say the asset is locked. pretty please help.

[Solitude]

I've attached a file that has it set up....

It also has a 'fade' option which allows for the vorticity value to fade out over time. It saves vorticity and vorticity_fade to the points.

Also in there is an example of using the vorticity to modify density, creating an effervescent type of effect where the stuff in high vorticity floats up. I've also used that to create an 'oobleck' style sim (not in this file), by modifying viscosity where high vorticity means it stiffens up, and then since I have the fading value present, it goes back to a regular liquid.

h12_vorticity_solver_2.hip

Edited October 29, 2012 by Solitude

[Pazuzu]

Also you can calculate the curl vector (vorticity) in sop's (no sim needed). Here is the asset:

Thanks to Johner for this technique.

SOP_curl.otl

Edited October 30, 2012 by Pazuzu

[R_cyph]

Thanks alot guys! you've been a great help

[R_cyph]

Okay,

Now that I have a nicely working vorticity attr working. I'm looking for something like maya's cloud particle rendering or krakatoa's particle voxel rendering. Just a little volume sphere applied to each particle with per partical density and color

I watched the waterfall tutorial on the sidefx site

http://www.sidefx.co...2179&Itemid=259

Unfortunately, They're using a volumecloud shader with uniform sampling and apparently you can't alter things like opacity or density or color per particle. is there another Shader i can use so I can change density or color on a per particle level?

Edited November 6, 2012 by R_cyph

[R_cyph]

Also you can calculate the curl vector (vorticity) in sop's (no sim needed). Here is the asset:

Thanks to Johner for this technique.

Any idea why the SOP_CURL otl isn't working houdini 13?

[ikarus]

VDB Analysis can calculate curl from a vector field.

[Skybar]

You can calculate vorticity directly in the DOPnet when you are simulating. Take a look at the "Gas Vortex Confinement DOP", it uses the same steps, so you could just copy the first part of it (if you dive into the node). What you want to keep is "create_curl" and "create_curlmag", these two creates two fields. Then you want to keep "calc_curl" which calculates the curl of the vel, and then finally you want "get_curlmag" which calculates the length of the curl - this is the vorticity. After that you could just pop down a "Gas Field to Particle" to export the curl_mag (vorticity) to your particles. Voilá, vorticity.

[dayvbrown]

Just a little volume sphere applied to each particle with per particle density and color

 

 

Hey hey,

This is really simple to achieve, you can create a shader with a "Lighting Model" shop inside and set the model to "Isotropic Volume". You can then bring in Cd\Density\etc to adjust as you need.

 

This will render each point as a little volume sphere dependent on the pscale attribute.

 

Cheers,

Dave.