      ==> Stereo pairs can be generated by using either a shear operation or
      	  by using an angular offset.  Both have problems.  The shear distorts
	  bounding surfaces.  The angular offset displaces specular highlights
	  and totally breaks Z-clipping.

	- ISOLATE (object code 15) not yet implemented for quadric surfaces
	- Linear depth-cueing code (FOG 0) is not correct for parts of the 
	  scene behind a transparent object. This problem arises because a 
	  linear fog model does not correspond to reality. 
	  It would be possible to handle transparency correctly for an 
	  exponential fog model, but doesn't seem worth the effort right now.
	- Z-clipped objects cast un-clipped shadows.
	- The mixed Fortran/C calls to local() generate an interesting 
	  variety of compiler warnings because of inadequte type-casting
	  on the Fortran side.  
	- General quadric surfaces (other than ellipsoids) may cast spurious
	  shadows, and always fail to shadow themselves.
	- Explicit vertex colors take precedence over material colors;
	  (That's a feature, not a bug)
	- Labels with TeX-like escape sequences are always treated as Left-Align.
	- Angstrom symbol only loaded into Times/Helvetica fonts.
	- ribbon coloring scheme 6 doesn't work
