KOffice.org

• Krita-Plugins, this project contains more tools and filters for Krita.
• Developing Krita Plugins – also a work in progress.
  A manual on writing C++ plugins for Krita.
• Manual – a work in
  progress, but rapid progress. By Sander Koning, Boudewijn Rempt, Casper Boemann and Cyrille Berger.
• Developing Krita a high-level overview of the architecture of Krita
• Painters and Paint Devices for information on the 2D canvas library that is at the heart of Krita

Free paint applications:

• MyPaint (sketch application optimized for tablet + keyboard)
• Gogh (sketch application optimized for tablet + keyboard)
• The Gimp (The GNU Image Manipulation Program)
• GSumi (Simulation of brush or pen and ink drawing)
• Wet Dream (Watercolor paint simulation), see
  also An Architecture for “natural” brush types.
• A Gimp Brush Proposal — never
  implemented, I guess, but interesting nonetheless.

Academic papers:

(These dissertations are made available for non-commercial purposes by Bill Baxter on his projects webpage)

• Wet & Sticky — dissertation by Tunde Cockshott on modelling wet paint.
• Applying Color Science to Computer Graphics — dissertation by Kenneth Paul Fishkin.
• Physically based interactive painting — dissertation by Bill Baxter.
• dAb Interactive Haptic Painting with 3D Virtual Brushes
• IMPaSTo – A realistic, Interactive
  Model for Paint