Simulated impasto: possible?

[achadwick]

Would it be possible to add support for faked impasto in the brush engine? Simple stuff like repeating dabs one or more times with different brightnesses:

(Public domain example of real-media impasto taken from Wikimedia Commons "Impasto-detailed_example..jpg"

I envisage it working by adding some extra settings

• num_repeats: float rounded to integer, the number of times a dab repeats with the same basic calculated size, position, fuzziness, pixel snap etc. Default & min 1.0; max ~10?
• dab_offset_dx and dab_offset_dy: offset of the dab from its basic calculated position, floating-point multiples of the actual (or base?) brush radius; default 0.0.

and an extra input which could be used to drive HSV/HSL/whatever lightness output as well as dab offset:

• repeat: the number of this repeated dab. Zero or one-based?

The applications could be quite interesting. Star scatterers too, if dab angle is allowed to vary by repeat number.

[jonnor]

You'll need to just try it out I think. The tricky bit here is finding an algorithm which can sensibly emulate the desired effect, defining the settings and inputs is not so hard...
If it can be done using the concept of 0 or more dabs, parametrized by size,opacity,position etc then the MyPaint engine can do it without mods to the surface or stroke interfaces.

[iirelu]

Simulating that is really hard, because to have any degree of believability you have to actually have the brush engine think in three dimensions, and think about lighting as well. Just having a sort of displaced-border effect isn't something I think would work.

[americogobbo]

I've found very interesting this idea to impasto... and I'm trying to create a small brush set to Gimp interpreting this concept. I'm not sure, but I think that is possible to use a .gih brush and a paint dynamic to try emulate, in part, this concept. Here some doodles with these previous experiments:
https://plus.google.com/+AmericoGobbo/posts/VjBcCrMvvc4