Overdrawing: Often it is not intended to paint wet-on-wet, the colors may mix in an unpredictable way or the paper might even crimp due to too much ink. Therefore regions where strokes have been applied are avoided for a predefined and color-specific time duration. This is done by intersecting di(T,C) with a map R that shows recently painted strokes. The resulting map Mi=R∩di(T,C) specifies the regions where new strokes can be placed.