Sticking moving particles to a deforming surface

[ndeboar]

Hey,

See attached. 

How would I get the particles to stick to the surface of the deforming tube, while still flowing over it? The volume gradient  & cross product vector works nicely when it's static, but falls apart when I add deformations.

Ta,

Nick

 

noodle_v3.hip

[Sean-R]

Hi Nick,

You can do a volume sample to get the particles offset from the sdf, multiplying this with the volume gradient will give you a vector. Adding this vector to the particles position will move it onto the surface, the vector will have to be negated to work correctly.

noodle_v4.hipnc

[ndeboar]

Makes sense! Cheers.

[iFight4theUser]

If the geo is too complex or thin for VDBs you can try using xyzdistance inside the solver to pull the nearest surface position. You'll need to recalculate your velocity vectors afterwards though, so not as elegant as the VDB solution. Nice example Sean the volume gradient idea is really clever.
 

int primID;
vector primUVs;
xyzdist(1,@P,primID,primUVs); // get the primID and primUV of the nearest prim on input2
@P = primuv(1,"P",primID,primUVs); // move the P to the position on that primitive