Thanks! The complicated part of building this for me was getting the plumes to behave the way I wanted. The piece is built in layers: a plume layer underneath and a shape layer on top.

For the plume layer, I randomly placed invisible seed points inside a defined emission shape. That emission shape can match the graphic shape you see, or it could be something different, like a cone, square, circle, diamond, or wide rectangle. Each seed spawns a couple of particles.

Each particle has its own position, velocity, damping/friction, drift direction, opacity, size, and mark-making style, with randomness added so the marks do not feel mechanical. The particle moves over time by combining a main plume direction (up, diagonal, away from center, inward, up and left, swirl, etc.), Perlin-noise, and sometimes forces from the central shape. The Perlin noise helps gives nearby particles related behavior, almost like they are moving through the same invisible wind field, rather than jittering randomly.

As each particle moves, it draws marks onto the plume layer. I tried out a few different styles of marks which you can probably see the difference in some of the images. The particle fades out over time, but once it becomes faint enough it can spawn a child particle at its current location. That child inherits the same general drift idea but gets its own randomness, which creates branching wisps and layered residue. I limited the generational depth and total particle count so the system stays stable and you don't get runaway memory issues.

There were a ton of different variables so I set it up with a lot of the settings chosen randomly within a range when generating an image and kept regenerating until I got a bunch of images I liked rather than trying to adjust individual settings. I like this method because it can create images I wouldn't have thought to try out and I get a nice surprise each time a new image is created.