Particle fluid based on subset of "Geometry" data

[~nature~]

Hi,everyone,I wonder if there's a way or trick to make the particle fluid solver only affect the subset of the imported Geometry.I mean based on some point attribute(Like Cd).any suggestion would be appreciate

Edited April 26, 2010 by ~nature~

[old school]

Can you be more specific? You only want to have the particle fluid solver to work on some points? And what do the unaffected particles do? Do they follow POP rules?

You can add the point attribute "fluid_forcescale" to diminish the effect of the Particle Fluid Solver and allow POPs to gain more control of the particle behaviour in the simulation.

See the help:

http://www.sidefx.com/docs/houdini10.0/nodes/dop/particlefluidsolver

and scroll down to the Internal Forces Tip on fluid_forcescale.

You could use an Attribute POP to pick up the color to set the fluid_forcescale attribute.

Edited April 28, 2010 by old school

[~nature~]

Can you be more specific? You only want to have the particle fluid solver to work on some points? And what do the unaffected particles do? Do they follow POP rules?

You can add the point attribute "fluid_forcescale" to diminish the effect of the Particle Fluid Solver and allow POPs to gain more control of the particle behaviour in the simulation.

See the help:

http://www.sidefx.com/docs/houdini10.0/nodes/dop/particlefluidsolver

and scroll down to the Internal Forces Tip on fluid_forcescale.

You could use an Attribute POP to pick up the color to set the fluid_forcescale attribute.

Hi,thanks very much for your reply

The problem is caused by the situation where in SOPs,I have the orginal point animation which accumulates the points in amount(e.g. at frame 1 ,the number of points is 1,at frame 100,is 100),what I want to do is hand over the points to the particle fluid solver to process it at each simulation timestep.that is once some of the point emerged,it drops and interacts like water.This can be easily achieved in POPs by the "group" node,but it's hard for me when comes into DOPs.as the SOP Geometry either take the inital state or refresh and flush the Geometry data at each time step which is not possible in this case.

I haven't noticed the "fluid_forcescale",I'll have a try

[~nature~]

Hi,thanks very much for your reply

The problem is caused by the situation where in SOPs,I have the orginal point animation which accumulates the points in amount(e.g. at frame 1 ,the number of points is 1,at frame 100,is 100),what I want to do is hand over the points to the particle fluid solver to process it at each simulation timestep.that is once some of the point emerged,it drops and interacts like water.This can be easily achieved in POPs by the "group" node,but it's hard for me when comes into DOPs.as the SOP Geometry either take the inital state or refresh and flush the Geometry data at each time step which is not possible in this case.

I haven't noticed the "fluid_forcescale",I'll have a try

I have tried it,but it seems the particle fluid solver only take into account fluid_forcescale at the inital frame again due to the SOP Geometry. Is there any way to approach such problem.

[old school]

Here's one approach where you spoon feed SPH with particles based on a condition.

Then when you build your fluid surface, merge in the particles before the condition along with the SPH fluid points.

See the attached example file.

emit_sph_fluid_from_particles.hip

[~nature~]

Here's one approach where you spoon feed SPH with particles based on a condition.

Then when you build your fluid surface, merge in the particles before the condition along with the SPH fluid points.

See the attached example file.

Thanks very much for your help

I see your hip files,but what I mean is directly convert such points as they are into particle fluid rather than emit from it and may add more points in the same particle fluid in the future due to the increasing amounts in the original point animation.any suggestion here？

[~nature~]

Thanks very much for your help

I see your hip files,but what I mean is directly convert such points as they are into particle fluid rather than emit from it and may add more points in the same particle fluid in the future due to the increasing amounts in the original point animation.any suggestion here？

It seems that the popsolver can approach this problem and add the particle to particle fluid obj in the mid sim based on some specification.but It's pretty slow ,unstable and hard to control.did I miss something or maybe another solution?

finally I solve this problem in the realflow via the python command such as emitter.addParticle(position,velocity). But still want to see the houdini way.

[old school]

I have tried it,but it seems the particle fluid solver only take into account fluid_forcescale at the inital frame again due to the SOP Geometry. Is there any way to approach such problem.

The SPH fluid solver is wired up to pass the results through POPs at each timestep (if you set it up from the shelf that is...).

You can read and modify the fluid_forcescale attribute in POPs dynamically.

[~nature~]

The SPH fluid solver is wired up to pass the results through POPs at each timestep (if you set it up from the shelf that is...).

You can read and modify the fluid_forcescale attribute in POPs dynamically.

Thanks again old school.Do you mean in the popsolver using the fluid_forcescale? but it only influence the internal force. In this case the particles with fluid forcescale 0 will still drop like ordinary particle under the external gravity force.I tried to apply the force in the popsolver but for some reason it doesn't work.