Fluid from moving creature

[Annon]

Hey everyone,

I'm after creating a creature made out of water and am wondering the best way to approach it.

Currently I have created a simple scatter+mesh setup, but would like gushing water to run down the body and back into the floor etc.

I'm sure there are loads of ways to create this (I'm playing with some ideas), but just wondering how some others might approach it.

Thanks

Christian

[lukeiamyourfather]

My first attempt would be with a POP network and the particle fluid surface node (to make the mesh for the fluid). If the POP network doesn't get a fluid enough look then SPH would be my next step. Though SPH seems excruciatingly slow in Houdini compared to RealFlow so I'd work in that application if possible.

[edward]

If the POP network doesn't get a fluid enough look then SPH would be my next step.

What about FLIP fluids?

[lukeiamyourfather]

What about FLIP fluids?

FLIP is best suited for large bodies of water. The velocity data for FLIP is carried through a grid which tends to lose small details and intricate motion.

[pclaes]

Have a look at this thread, it has a really nice example of an object made out of sand - might work for your liquid too:

Flip has problems with containing the volume too, but it is a lot faster and more stable than SPH. If you do require extra detail, splashes etc... I would recommend to mix in (birth) extra particles (from other sims). Eventually you end up with a pointcloud, it does not really matter where those points come from. If you find you get nicer splashes with sph, or even procedurally model them (sheets of water), that all works.

[Annon]

Thanks everyone, I'll check out the sand girl tomorrow.

So far I've got a pop sim running down the character, sticking to the surface (SDF) with a VOPSOP.

It's definitely heading in the right direction, but I'll be looking at combining it with other methods to complete it I think.

I'll get back on here when I've sorted a few things out with it.

Thanks

Christian

[Yassine]

Hi everyone,

first post, first embarrassment..

I'm shaping a human head with fluids propagating from the forehead. I have scattered the mesh of points with the scatter node and then starting from one single point I have created a propagation making points look for the nearest ones. I've applied Flip Fluids and created a second emission of particles from the same propagating points to add some extra details.

So far everything works pretty nicely if the mesh doesn't deform, but my character is also rigged and consequently the mesh deform. Apparently the scatter node applied on a deforming mesh reposition points every frame and this brake the reference for my propagation. I was wondering if anybody has an idea on how to stop the points scattered on the surface in the first assigned position and keep them in place during the deformation of the mash.

Many thanks,

Yassine

[pclaes]

So far everything works pretty nicely if the mesh doesn't deform, but my character is also rigged and consequently the mesh deform. Apparently the scatter node applied on a deforming mesh reposition points every frame and this brake the reference for my propagation. I was wondering if anybody has an idea on how to stop the points scattered on the surface in the first assigned position and keep them in place during the deformation of the mash.

This is a very common problem, look up "rest position", "measure area" and "scatter on deforming geometry" - it would surprise me if there is no example of this in the scatter sop help file.

Generally what you do is measure the area of your mesh on frame 1 and copy the area attribute back onto the moving mesh, you then scatter based on this area attribute. You can get frame 1 with a timeshift, measure the area with a measure sop and copy the attribute with an attributecopy sop.

[Yassine]

This is a very common problem, look up "rest position", "measure area" and "scatter on deforming geometry" - it would surprise me if there is no example of this in the scatter sop help file.

Generally what you do is measure the area of your mesh on frame 1 and copy the area attribute back onto the moving mesh, you then scatter based on this area attribute. You can get frame 1 with a timeshift, measure the area with a measure sop and copy the attribute with an attributecopy sop.

Oh, I see. Thank you very much.

I haven't found many example about this, but it's mentioned in "Houdini On The Spot".

[Annon]

Just turn off "Scatter Based on Primitive Area" and the points will stick to the mesh.

Hope this helps

Christian

[ikarus]

just kind of an odd idea I had about this

do simulation on non-animated geometry, calculate deformation on geo (Pos-restPos), transfer deformation value to particles and apply deform (Pos+deform)

maybe helpful idk

edt: i would only have either the deform or transform on at a time, not both

deformApply.hipnc

Edited May 2, 2011 by ikarus