TODO

consider more user-friendly alternatives to AntTweakBar
consider making keyboard shortcuts more sensible and comprehensive
color model: consider if intensity is calibrated and adds correctly
             is there a better way to map complex argument to color?
try using a fixed set of vertices
look at more ways to make subdivision faster
  presently, we do way too many function evaluations trying to find
  the best place to insert the next point
examine what precision is needed in the various textures
look at what version of OpenGL is strictly required, and see if
  various features can also be used via extensions, so as to lower the
  OpenGL version requirement
research the possibility of depth sorting and obscuring background
  clouds
handle tetrahedra with a face seen edge-on
clean up all error handling