At SOP level I can do a scatter on any geo and then send those into a Particle SOP, putting a Sort SOP inbetween I can rather easy achive diffrent “pealing off” effects with Particle SOP set to Modify Source geo but I have no idea how todo this at POP level.

Putting Impulse Activation to something like $FF == 1 and Impulse Birth Rate to 5000 will spawn 5000 particles from frame 1 looking sorta like scatter but they all start to simulate at the same time.. how would I go about in POP's achive what is so easy todo with Particle SOP ?

/M

Hello Magnus,

Couple of things to experiment with:

(1) you can use $NPT (number of points in the source geo – assuming you are birthing from points) in the impulse birth rate to birth the exact number of particles that you scatter
(2) if you set your birth emission type to points(ordered) your particles' $ID attribute will be set according to your point sort order so you can still rely on your sop-based sort order.
(3) you can animate group membership and have particles ‘peel off’ based on their group. So: create a group, add particles to group over time (using say, fit($FF, 1, 100, 0, $NPT) >= $ID). apply forces to ONLY particles in the group.

Holler if you need more hints,

Best,

G

ps: keep up the good work – your questions are showing an ever-increasing understanding of the mechanics of houdini.

Hey thanks Keyframe !

I actually came up with solution 3 later, but didnt realy like it because I have to put the group name in all the following POP's but I guess I just have to get over it

A follow up on that, would it be possible to somehow suppress $AGE increasing untill they are in the new group ?
Because I would like to use $AGE to base how much they later are affected by a attractor POP.

Maybe use the group node to create 2 groups, “stay” and “leave” and with a Suppress POP ?

/M

ps: Thanks I love learning this software, and Im starting to understand some of the “oooh how did they do that” from movies.

Take a look at the attached file – it shows how to scale a force (in this case, drag) based on supressed aging rules – that become ‘unsuppressed’ over time.

Cheers,

G

Ah suppress age is a bool, but ofcourse

I got it to work sorta like I wanted now, it's pealing of and then based on age attracted to a collision object where they stick.

But enought talk here is the file

Thank!!

/Magnus

Ah suppress age is a bool, but ofcourse

yeah, I hear ya – the sliders are really misleading in this context…


G

BTW, using a attractor like in the scene in my previous post, is there any way to achive some sort of uniformed spread of where the particles land.

My first thought was to use the Interact POP but maybe there is a faster simpler way ?

/M