cube.ps

/Sleep {5000000 {} repeat } def

/P 50 def

/X 250 def
/Y 200 def

% rotation angles
/a 0 def
/b 0 def
/c 0 def

{
    % axis
    100 Y moveto 400 Y lineto X 50 moveto X 350 lineto 0.5 setgray stroke
    
    % vertices
    /v[
        [P neg P neg P neg]
        [P P neg P neg]
        [P P P neg]
        [P neg P P neg]
        [P neg P neg P]
        [P P neg P]
        [P P P]
        [P neg P P]
    ]def
    
    /v2 8 array def
    
    % sines/cosines
    /c1 a cos def
    /c2 b cos def
    /c3 c cos def
    
    /s1 a sin def
    /s2 b sin def
    /s3 c sin def
    
    % projections
    0 1 7 {
        /i exch def
        /p v i get def
        /x p 0 get def
        /y p 1 get def
        /z p 2 get def
        
        % rotations
        /ty y c1 mul z s1 mul sub def
        /tz y s1 mul z c1 mul add def
        /tx x c2 mul tz s2 mul add def
        /tz tz c2 mul x s2 mul sub def
        
        /nx tx c3 mul ty s3 mul sub def
        /ny tx s3 mul ty c3 mul add def
        
        v2 i [ X nx add Y ny sub ] put
    } for
    
    % draw edges
    [[0 1][1 2][2 3][3 0][4 5][5 6][6 7][7 4][0 4][1 5][2 6][3 7]] {
        /e exch def
        v2 e 0 get get 0 get v2 e 0 get get 1 get moveto
        v2 e 1 get get 0 get v2 e 1 get get 1 get lineto
    } forall
    
    1 0 0 setrgbcolor stroke
    flushpage
    
    Sleep
    
    1 setgray 0 0 400 400 rectfill % clear
    
    /a a 0.2 add def
    /b b 0.4 sub def
    /c c 0.6 sub def
} loop