Emmit via bitmap

Looking for finer control of particle emission, wondering if I can use a bitmap or procedural noise map to trigger the probability of emission on a mesh? Relatively new to Cascade, I could be missing something obvious. I see that a mesh can be used, which could work. Not ideal. Read an impressive thread showing how to map csv data to position by encoding positional data into bitmap, that could work too. Thread started veer from my goal when it got heavy into point cloud territory, but it looks like it could be paired down for my needs. Would be excellent to paint heat maps for particle emission.

Any ideas?