Glenz vectors
3 bitplanes

 COLOR01 := $eef = off white    
 COLOR02 := $306 = dark blue
 COLOR05 := $fff = pure white    
 COLOR06 := $63d = light blue    

Front white face:
 overlapping with back transparent faces is off white   - color01  bpl 1 0 0
 overlapping with back white face is pure white         - color05  bpl 1 0 1
 DRAW ON BPL 1 (COLOR01)

Back white face
 overlapping with front transparent face is light blue  - color06  bpl 0 1 1
 overlapping with front white face is pure white        - color05  bpl 1 0 1
 DRAW ON BPL 3 (COLOR04)

Front transparent face: = 0 1 0 = 2
 overlapping back transparent is dark blue              - color02  bpl 0 1 0
 overlapping back white face is light blue              - color06  bpl 0 1 1
 DRAW ON BPL 2 (COLOR02)

Back transparent face: = 0 0 0 = 0
 overlapping front transparent is dark blue             - color02  bpl 0 1 0
 overlapping front white faceis off white               - color01  bpl 1 0 0
 DON'T DRAW

Use color 1 (white), 2 (trans) for visible faces
Use color 4 (undefined), 0 for back faces

This means that each face is actually drawn on ONE bitplane.
