Quite complex, but not impossible for Grasshopper, I think …
(two attached images)
It will be possible in some way, to achieve those “effects of falling water and pigment” together, as if they were on an applied paper
? - as if it were watercolor and water -
Even sometimes, of course, mixing with another second or third color?
Also control the direction of the fall and quantity of the water.
(Of course, the steeper the steeper, and even one inclines more towards another direction at some point, changing the pigment fall towards one or another part of the surface, or paper in reality)
I don’t have much idea, how to approach that, or how to investigate looking for a possible solution …
(… normally, there is nothing so ‘sophisticated’ in Digital Painting programs, like ArtRage, or Sketchbook …).
I would be interested if someone has any possible approach.