tag geo that exceeds vel mag threshold as always 'on' subseque

[gnarlog]

Hello there,

 

I would like to take an alembic imported point cache and turn on the vertices based on some velocity magnitude threshold using a delete sop, but have them not turn back off(get deleted) when the velocity magnitude goes back below that threshold. I know this kinda thing is doable, but I suck at houdini. If anyone is feeling charitable, I'd really appreciate it.

 

Thanks a lot,

 

Matt

[narbuckl]

There are many ways to do this but if you just want to use a delete sop, make sure that your imported alembic is converted to either polys or points (you can just drop a convert node down after the alembic node if your uncertain) and has a velocity attribute (if it doesnt then drop down a trail attribute and set it to compute velocity) then set the delete sop to expression and use something like
length($VX,$VY,$VZ) < 5

getting the length of the velocity vector will basically give you the speed then its just about what you want the cutoff to be.

 

-N

[eetu]

Here's a simple example, done with a group node inside a Solver SOP. The expression solution doesn't scale too well, if speed is an issue do the velocity calculation and grouping inside a vop sop.

 

ee_velocity_reveal.hip

[gnarlog]

Thanks for the responses! Eetu, that is exactly what I was after. Thanks again!