View Full Version : Unnatural FLIP behavior with Collision Geo

03 March 2013, 01:34 AM
I am working on a scene where FLIP is poured onto a character. I am wondering why the FLIP particles are doing a couple of things:

*Why the particles are exploding so much in all directions on first contact with the collision geometry? I was told that it may be the little details on the character geometry like the mustache, those pinches between the arms and shoulder, etc. that could be the problem.

*Why the FLIP particles unnaturally wrap around the character geo as it is moving forward. Itís almost as if the FLIP fluids try to meet again after being separated.

Example Link (

03 March 2013, 01:37 AM
make sure to inherit some of the velocity from your collider, make sure that your resolution is high enough if you are doing volume collisions, make sure that the normals are facing the right direction, make sure that the scale is realistic and make sure that you are using enough substeps for the motion. I like to use a combination of flip and dumb particles (ie dumb particles when they are stuck to the surface and flip when they fall off or flying towards the surface to keep things moving fast.

try using the stcikiness parameter as well.

03 March 2013, 11:46 AM
use a SDF as collider is the way to go with the flip solver. If your collision geo is animated use the trail sop to compute velocity vectors then use (under populate containers) the shelf tool "collide with objects". Check the div size in the fluid source sop for correct detail of your character.

03 March 2013, 10:02 PM
Thanks Felix. I have tried out your method, but the flip goes right through the object.

Here is my current process: My character is a .bgeo file that was rop cached from an Alembic import. I then used a file sop to bring in the .bgeo cache, attached it to a trail with the velocity setting, and then to an isooffset sop (set to SDF Volume, Ray Intersect, Div Size: 150). I then rop cached the sdf, file imported, and directed a Source Volume volume path to the imported SDF file.

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03 March 2013, 10:02 PM
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