Make particles follow lines or grids

[chaindriver]

Hi,

I'm trying to get particles to move along lines and grids. Is there any particular way this can be done?

[gui]

yes. Create normals tangent to line (use a poli-frame sop, and change tangent name to N), and use those tangents to drive de velocity of particles.

In a pop-vop, use a point cloud open to import the normals of the line, and add that to the velocity. If you don´t know how to use point clouds in houdini, try seeing peter quint´s great tutorials in this subject first.

You can create forces in the points in the line to drive the simulation, but in my experience, is far more difficult. Try adding a point sop in the line and change parameters in the forces tab. Then, in the pop net, use an attractor to feed the forces into the simulation.

[chaindriver]

Thanks for the tips Gui! I'm trying them out now!

[gui]

welcome! the benefit of using point cloud is that it interpolates the attributes (in this case, the normals in the curve), so you wont need too many points, but make sure that the point cloud radius encompass some points of the curve.

[chaindriver]

Got it

[eetu]

Last time I had to do this I needed it to be very precise and controllable, so I ended up creating the grid/lines and then just carving points from those lines. It's not instant gratification either, takes some twiddling to get what you want, but there will not be any unwanted surprises like there can very well be with a simulation..

So, Carve SOP with animated parameters might be your friend - it all depends, as always

[Scratch]

Use a creep POP, it does exactly that!

http://www.sidefx.com/docs/houdini12.1/nodes/pop/creep

[stig_olsen]

eetu, is this still valid? or do you have better ways to do this today?

Can you walk med through this way?

 

Stig

[eetu]

Here's a quick hip to illustrate the idea. I did the crawling dots on this alien artifact in this way. In fact they are short line segments, but that's trivial with this technique - just use ch("domainu1")+0.01 or somesuch in the Second U parameter in the Carve SOP.

ee_grid_crawling_particles.hip

ee_grid_crawling_particles.mov