Actually Deep Paint 3D was written before Deep Paint 2d, back when Deep Paint was known as 4D Paint.
The 2D version just uses a specialization of the 3D rendering proc.
But in my opinion (as I was the guy who wrote all the rendering and paint technology in Deep Paint) it's slow as a dog, and apalling quality.
I've got better at graphics since then...
In ArtRage as a workaround for not liking top-left lighting, you could rotate your canvas before you start painting by 90 or 180 degrees. Then when you do the export, use another application to rotate the ouput to the same orientation.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"