Hi

Have a simple DOP network for emitting particles from a mesh source.

Right now when I add a gravity force the particles emit even when the mesh emitter is not moving.

How can I modify this, perhaps with a VEXpression, so that gravity only affects the particles when the emitter is moving?

Here's a file that shows one way to do it.

Keep in mind your asking for two things, when to emit or not, and when to apply your negative y popforce value.

I made a null node with parameter to set the threshold value.

The sovler sop creates a velocity value and creates an attribute called threshold which is applied in the next pointwrangle to the point.

The popforce node is set to use vexpressions and the negative y force is only applied once threshold is passed.

The POP Source nodes Impulse Activation paramter is set with python to only activate if threshold is passed.

P.S. I am not experienced that much with pop networks, so keep eyes peeled on this thread as someone might post a better solution.