Hi, i'm new here and it´s my first post. I'm learning houdini on the fly, as I need to do some reserch for sand fx, and houdini is the best I saw for this purpose.
So i've build my scene, I have grain falling down from the tree and I was going to apply popwind for particles with turbulence noise, the sim looks amaizinly well hovewer after particles falls down the tree the motion of the particles is little bit strange, its very visible the patern of the noise where they are movin on, probably i have to animate the noise patern but didnt find nothing like that.
So i decided to apply the wind ONLY over the particles wich are still laying down on the tree until thay starts to fall off. So i created the group with bounding box but the problem is those particles beeng already in that group have the attribute applied to it even than they come out of that bounding box and still are influenced by wind force, so i dlike to exclude those one falling out of the bounding box from the wind but cant get to manage how to do that. I thought i need to make another groupe to exclude those particles or I need some expression?
I created another group but cant understand how to perform the math to exclude one group from other and than applye it to the wind. Hope someone can help me. Thanks

The wind node may have a Group field. This will limit the wind to affect only candidates found in that group. Type in the name of your group in that field or select it from the drop down.

Enivob
The wind node may have a Group field. This will limit the wind to affect only candidates found in that group. Type in the name of your group in that field or select it from the drop down.

Hi thanks for your reply! thats right, I did so, but, the particles ramains in that group even when they comes out of the group bouding box, how do I remove them from group when they comes out from it?