For this, I added a system that spawns particles along the trail, and these particles deposit a bit of snow while they fly, with less and less snow being deposited over time as they fade out. What's cool about this is that the snow initially comes from the mass that the trace removed, so the total amount of snow stays the same. I also added a smoothing algorithm on top of all this. There's no parallax here, but I'm currently working on adding that.

Bigger video here: https://youtu.be/pfaewyfFrKM

Can be played with here:

https://dirtnap.parttimemonkey.com/sandbox

Lemme know if you simulation people know how to make it better or more interesting to play with!

Finally found time to implement it. Footage from our multiplayer sandbox game called BFS. The simulation is deterministic for multiplayer to work