Delete scatter points based on time

[cowboy71]

Hey guys,

Quick question about deleting scatter points.  I have a character walking over a grid and transferring red to scatter points on the grid.  So his foot steps are in red.  His foot stays down on the grid for about 2 seconds 

before he continues his walk cycle.  The red particles are piped into a popnet which is emitting particles.  Problem is those red points keep emitting particles and not just a burst.   I'm trying to either delete those red points almost instantly but long enough for the popnet to emit once, or emit only once from the red points.   He does this throughout the animation,  so I don't think I can use $FF.  Kinda new to Houdini,  so maybe I'm not thinking about it correctly.

 

Thanks    

[Stephen Moroz]

Hey, I'm sure there's a MUCH simpler way of doing this, but I'm tired and this way kinda works, so hopefully this is of some use to you!

deleteScatterPoints.hipnc

I'm essentially just using a solver node to test each point to see if it's red on both the current and the previous frame, and if so, create and set a "kill" attribute to be 1 (the rest will be 0 because that's the default for new attributes). Then after that, I just delete any points that have a kill attribute of 1 (and also any points that aren't red).

Then in the pop network, I just set the source to "all points"

Hope this helps!

(although like I say, there's probably a much simpler way!)

[cowboy71]

This is perfect.  I know there are so many ways to achieve an end result in Houdini,  but this is exactly what I was looking for, and I learned a bit more

about the Sop solver. 

Thank you so much!

[Stephen Moroz]

No worries, glad it helped!