There are some brushes like Classic/Marker Fat that use elliptical dab angle modified by Ascension to basically achieve a rectangular-shaped point that is always thinnest when the tool movement (direction) is parallel to the tool direction (ascension) and widest when the strokes are perpendicular to the tool direction. But what if you want to modify other brush settings like Jitter or Radius based on this direction/ascension difference (Angle of Attack for lack of a better term)? It seems like a new input is needed, derived from ascension and direction possibly. Maybe a sensible range would be 0-90 degrees where 0 is parallel movement and 90 is perpendicular. If it is possible to calculate, it might be nice to have 0-180 where 0 degrees is movement in the same direction as tool ascension and 180 is movement directly opposite of tool ascension (pushing vs dragging).
With this input you might be able to design a brush that behaves different when “dragged” versus when “pushed”, like the bristles on a real brush that become fuzzier when pushed. Or the smooth flow when dragging a fountain pen versus the skips you might get when pushing. Another idea is a pencil brush that, when tilted sufficiently, begins to have more jitter but only when the strokes are perpendicular to the direction of the tool. This would make it much easier to transition from line to tone in the same stroke and be great for simulating charcoal, conte crayon, etc.
Is anyone else interested in dynamics like this?