I can never remember how glDrawArrays counts things
GPU depth blending works (almost)

The almost is because we're not blending global z-depth yet.
Use global z values for height-map blending
Separate into raster and GL paint functions
Working on framework to switch between raster and GL rendering
More work at supporting both backends
Raster engine still works
Add menu option to switch between raster and OpenGL

Unfortunately, when switching to OpenGL, UI elements (view selector
and status text) disappear.  This is likely due to a limitation
discussed in the docs: "On Mac OS X, when Qt is built with Cocoa
support, a QGLWidget can't have any sibling widgets placed on
top of itself.""