This renderer was developed as part of my Master's thesis at Princeton University. You can find the original thesis here.
Non-photorealistic rendering is inspired by the expressiveness of animated cartoons, paintings and drawings.
Other techniques draw upon traditional information graphics, where clarifying shape and structure are superior goals to lifelike depiction.
While non-photorealistic rendering internally requires a very different rendering infrastructure, the renderer is seamlessly integrated with Processing and doesn't require learning new concepts or a new language. Non-Photorealistic and ordinary Processing OpenGL rendering can be mixed in one sketch.
As opposed to the Processing OpenGL renderer, this renderer is completely hardware based and offers a considerable speedup compared to the original PGraphicsOpenGL renderer when using 3D models and makes full use of GLSL shaders.