got it figured out. I had little knowledge of the particleSampler node and didn't realize it takes no input, it just samples the scene. After that it was just a matter of connecting the sampler to...

an update: After much searching, I found that other people have found a solution to this and that solution is the particleSamplerInfo node.

after all my reading, it seems all I need to do is input...

I have a volume emitter set to cloud s/w for the particle type. I have an opacityPP attribute set to use a ramp for the opacity which is using a value of 0 at birth, 1 somewhere in the middle, and 0...