Flips Activevalue

[Hoyt]

Hi Guys!

i`m trying to use the activevalue node in dops to drive a flips sim: using color in sops to set the active value of every simple particle. like i would do with a RBD object.

 

but at the end it doesnt work.

 

i would appreciate any help

 

the idea its to drive the flips sim using color to the set te active value.

 

thanks in advance

active_flip.hip

[danw]

I'm pretty sure FLIP fluids don't work that way.  You can activate a FLIP object - that is, the object that contains the entire particle stream, but the individual particles aren't handled as individual objects... it would make it impossibly heavy, and cause rather strange behaviour too I think.

 

If you want particles to remain static, before being "activated" in the sim, you need to group just the points you want to activate at a particular frame from a SOPs point cloud, and use them as an emitter.

If you want those particles to be present in the sim from the start - as in, collidable, but static, then it's a rather more difficult notion.  About the best way I can think of is to give those particles a massive viscosity value, and maybe use a gravity mask to stop them falling under gravity.

 

Basically, complicated.  It may be better to try and re-think your approach.  FLIP fluids behave like fluid, often even when you're trying everything possible to make them do otherwise... you can waste a LOT of time trying to invent ways to stop FLIP fluids being fluid :-)

[sekow]

 you can waste a LOT of time trying to invent ways to stop FLIP fluids being fluid :-)

 

gonna tattoo this on my neck, for every hovering AD behind me

[johner]

If you want those particles to be present in the sim from the start - as in, collidable, but static, then it's a rather more difficult notion.  About the best way I can think of is to give those particles a massive viscosity value, and maybe use a gravity mask to stop them falling under gravity.

 

You can do some... interesting effects by enabling Force Override on the FLIP Solver and setting the ballistic attribute on the particles. That attribute controls the degree to which particles are affected by the fluid velocity; however they still contribute to the pressure solve, even if completely ballistic.  So other FLIP particles will react to ballistic particles, while the ballistic particles can be manipulated in all sorts of strange ways.

 

Attached is a very simple example of making a "dam" out of ballistic particles. One potential snag is if you fade in your ballistic value as in this example, the slightly ballistic particles will start to compress as they are less and less influenced by pressure.  At which point our old friend Reseeding kicks in and starts deleting them.  So you might have to tweak those values or turn it off.

ballistic_dam.hip

[JuriBryan]

sopsolver, read in the first frame they exist, vopsop, first in put is current frame second the static frame, import attribute based on id grabbing P, pipe P old to current P and set v to 0,0,0.
build in a switch based on a frame or color from that set up to standard.
now you have per point activation driven by what ever you want.
does not work with reseeding on and a emitting fluid... you need the same id values on the static points as you have on the current ones.

 

Cheers,
Juri

[scorpes]

On 8/21/2014 at 10:09 AM, JuriBryan said:

sopsolver, read in the first frame they exist, vopsop, first in put is current frame second the static frame, import attribute based on id grabbing P, pipe P old to current P and set v to 0,0,0.
build in a switch based on a frame or color from that set up to standard.
now you have per point activation driven by what ever you want.
does not work with reseeding on and a emitting fluid... you need the same id values on the static points as you have on the current ones.

 

Cheers,
Juri

Where do you put the sop solver? Inside Dops?

[KlhavKalashFX]

On 20/08/2014 at 10:52 AM, danw said:

I'm pretty sure FLIP fluids don't work that way.  You can activate a FLIP object - that is, the object that contains the entire particle stream, but the individual particles aren't handled as individual objects... it would make it impossibly heavy, and cause rather strange behaviour too I think.

 

If you want particles to remain static, before being "activated" in the sim, you need to group just the points you want to activate at a particular frame from a SOPs point cloud, and use them as an emitter.

If you want those particles to be present in the sim from the start - as in, collidable, but static, then it's a rather more difficult notion.  About the best way I can think of is to give those particles a massive viscosity value, and maybe use a gravity mask to stop them falling under gravity.

 

Basically, complicated.  It may be better to try and re-think your approach.  FLIP fluids behave like fluid, often even when you're trying everything possible to make them do otherwise... you can waste a LOT of time trying to invent ways to stop FLIP fluids being fluid :-)

If you use a Pop Source you can emit by attribute