dependencies on the 2D:

view.c:      gets aspect ratio from grd_cap->aspect
ctxtguts.c:  sets the 2d canvas with gr_set_canvas
primfunc.c:  uses internal indices into grd_canvas_table
             references grd_canvas_table
             references gr_null and gr_silent_null
             (we copied grnull.h into the r3d tree to get them)
primmisc.c:  calls the 2d line drawer and gr_set_fcolor
