How to move particles along surface normal?

[fragmentzero]

Hello,

I am trying a simulation where I need to move particles along normal direction of a surface.

Normal can be combed or perturbed using metaballs.

And the particles should take the direction of closest point's normal.

I have attached a file where I unsuccessfully use creep and ray sops.

But its far from what I want to achieve.

My goal is sort of a "flow direction" for spawned particles encoded in surface normals.

Any help is appreciated.

Thanks

Particles_Along_Surface_Normal_01.hipnc

[Akabane]

Just from the top of my head...

What about attribTransferring the surface N as Velocity for the particles each frame?

Delete it each frame and replace it directly with the nearest surface point velocity?

[fragmentzero]

Sounds like a valid thing to do.

I am trying to implement it but with some struggle as I am fairly new to Houdini.

Can you please give an example when you have some time?

Thanks

[ford77]

Probably it will be the point sop. Set up the parameters on the force tab

and use the grid as an attractor in the pop network. probably a drag

will help too.

[mawi]

Import the surface as a point cloud and filter the N attribute in a pop-vop.

Im not infront of houdini now so search for point cloud on the forums. There should be plenty of examples.

Else I might be able to do a simple file for you later on today.

[old school]

I whipped up a quick prototype file that uses perturbed surface normals and used a Fluid Source SOP to create vel fields from the perturbed surface normals then used an Advect Volume POP to push the particles about.

Lots more control and if you cache out the vel fields to disk, potentially way faster than point cloud lookups in to vel fields.

particles_pushed_by_surface_N.hip

[fragmentzero]

That looks interesting. I'll look into the file and Volumes + fluids.

Thanks