Learning Houdini: Distance To Surface

[artem-af]

I am trying to learn Houdini (work mostly with Maya) and sometimes I find that I just can't figure out how to do something. I thought posting here might get me past these roadblocks.

Right now I am trying to calculate the distance to a specific surface for each particle in a pop network. Once I have this I will kill out those particles that are more than a certain distance from the surface. Can anyone suggest a good way to accomplish this? I'm in Houdini 9.5. Thanks

[xavier]

There are a great many ways to do this in Houdini.

Probably the easiest and fastest method would be to take your surface you want to test against and offset it with a Point SOP (Position set to something like $TX + $NX*2, $TY + $NY*2, $TZ + $NZ*2) then use the Collision POP referencing the offset surface set to pass the particles through "Continue on course".
In the Collision POPs group field type in a name like kill_hit and toggle the persistent flag just to be sure.

Finally add a Kill POP and simply reference the group.
The nice thing about this method is that you can sculpt the collision surface, add warp deformations that are time based, etc.

You can also drive global events based on hits so you could run scripts, set parms, etc.

pm me if you want an example file.

-jeff