Snap surface points to another mesh, based on distance

Eg. When you have a simmed fluid not quite sitting on it's collision surface/ intersecting & you want it to be fixed/better.

Using a Point Vop. Plug in the surface and it's "collider".
Drop down a xyzdist plug that into a primitive normal. Hook up the appropriate inputs, don't for the the "file" input in the primitive normal. Set the max search distance to something sensible (probably a small value)

Plug the resultant "dist" from the xyzdist into a fit range node and promote the max value to the object level. In the destination value, set the min to 1 and the max to 0. Multiply this by the distance to avoid affecting the entire object (the max value will clamp a lot of values to 0 and nullify it)

Plug things into a displace along normal node. Promote the scale value. Finally connect the final P value.

It's worth having a group node with bounding points to check how well it's all worked.

sticky fields Houdini

Enable Sticky in the Flip Solver.
Create sticky attributes using point wrangle (f@stick=1;) and paint (replace Cd with stick).
VDB from polygons, using the attribute at the bottom of the node.

in the flip solver, add a SOP-scalar-field node and change the data at the bottom to "stick".

bounding box group node for faster VDB meshing

Group points, turn off numeric, enable bounding points & change bounding type to points only.
Blast away particles before VDB evaluation to save on computation time.

particle velocity to VDB fog/volume

particles, run a pointVop taking length of velocity and fit ranging them (min max to 0 and 1)
Plug new values into pscale.

VDB from particles, select fog, set minimum particle radius to 0.

should have a VDB mask ready for the faster parts of the sim.