Factor out texture lookup in fragment shader
Implement basic fragment shader

Just writes red for any rays that hit something. It doesn't seem to be
working quite right.
Loop through entire model, with transparency

Aww yeah, looking actually 3d now.
Implement bounds checking

texture was just wrapping around before
Implement better threshold cutoff

I don't *really* understand what's going on, but I'm getting there
Implement gradient calculation in model

Not sure if the code can be simplified further, but it appears to work.
Refactor and simply shader constants

am I pro yet
Implement Phong shading

Now for a proper transfer function
Factor out ambient intensity constant