isolating static particles

[borisb2]

Hi.

I'm retiming a bin-sequence from realflow to make a slowdown effect. It works pretty fine except for regions where new particles are born and houdini somehow interpolates so that I got not moving particles inside my simulation. If there would be a way to isolate these particles and delete them I could rexport that as a new bin-sequence.

Is there somethign like "last position" (like in maya) I could query? I had a look on other attributes but so far I couldnt isolate these static particles.

Thanks for any help!

[jacob clark]

Hi.

I'm retiming a bin-sequence from realflow to make a slowdown effect. It works pretty fine except for regions where new particles are born and houdini somehow interpolates so that I got not moving particles inside my simulation. If there would be a way to isolate these particles and delete them I could rexport that as a new bin-sequence.

Is there somethign like "last position" (like in maya) I could query? I had a look on other attributes but so far I couldnt isolate these static particles.

Thanks for any help!

Hi Boris,

Have a look at the 'v' attribute. This is the direction and distance to the last position of the particle. Also called velocity in Houdini. If the vector has a length of 0, you can be pretty sure it's stopped.

If 'v' doesn't exist, and you have a constant point count. You can use the Trail SOP to compute the 'v' on the fly. Hope this helps!

cheers,

-j

Edited December 6, 2010 by jacob clark

[borisb2]

man, you saved my life!!

Using the trail-SOP to compute the velocity (even if v was of course already in the bin sequence) let me group and delete the static ones.. What an amazing workflow - sim in realflow at 25 fps and retime/re-export in houdini later to ANY fps

Thanks a lot!

Edited December 6, 2010 by borisb2