OptiPaintThe Light Strokes OptiPaint system is the first input device that lets you use real paint brushes and other actual artists’ tools directly with your favorite paint software.
You can even use your fingers and hands, or virtually any light-colored object you’d care to paint with.

The OptiPaint system picks up the changing shapes and textures of those tools with each stroke.
Up till now, the only way to get real brushstrokes into a computer would be to paint them on paper, let them dry, and scan them in. Not exactly interactive. Now with the OptiPaint system, you can paint with real brushes in real time.