Today’s invention is to create a paint tool for Gimp or Photoshop which contains information about paint drying behaviour.
One could specify the properties of the paint so that a realistic drying time would be simulated. This would allow ‘wet’ paint to be manipulated for a while on screen.
It would also be possible to have such virtual paint exhibit smart features, such as a tendency to mix more with some than other colours or to flow depending upon the simulated canvas’ local absorption properties.
Paint colour might even be allowed to change on subsequent viewings, so that a digital picture could bleach realistically when viewed years later.