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Expression for 'New In Group' ?

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Like the title says, is there a way to tell if a particle just entered a group? Basically I want to set velocity of a particle on one frame... only when the particle first enters a specific group. Any suggestions welcome :)

Thanks!

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Maybe you can use the same expression you'd use to get the particles into the group. For example, if particles are in group when $TY>1 then, in the velocity field write the same expression...

Or you could write a python operator to compare the same group node at different frames... but I don't know exactly if it is possible or how...

Lots of times errors comes because bad approximation to resolve a problem.

Good luck!

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You know, I didn't really think of that (pretty retarded of me!) -- but here's my issue, though I still have to test.. I am using a voppop to set the group based on a condition, but I'm still wrapping my head around vops, and how to get it to set a value once, and then have my particles keep that value, not have it overwritten every frame (right now I'm trying with color, though I'll try with velocity tonight). If I have time, I'll post a file tonight to better explain what I mean.

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Maybe something like this? =)

new_in_group.hip

YES! That was it... and I kind of get it too! :D ...pretty simple, yet was such a pain for me to wrap my head around the logic (overall Houdini Pop logic) Thanks!

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