Rendering Erratta

I've been incorporating some tweaks to rendering. In addition to switching to OpenGL for rendering, I've added some embossing effects to give the paint the appearance of depth (though it's sort of a "fake" lighting effect and isn't really based on colour per se), and I've also added a bit more of paint fluid simulation (though simplified) with advection - that is, wet paint being moved around slightly when painting over top of it.

The advection can be hard to see, but looking at parts of the purple line(s) that have been painted over you can see that the purple paint has been smeared a little - probably most visible in this example looking at the white paint in the lower left and the yellow in the upper left.

I've also turned off the specular highlights on the canvas background (though it's still applied to the paint).