%!PS-Adobe-2.0
%%BoundingBox: 0 0 372 180

/w 372 def
/h 180 def

(ps3d.inc) run
(epsetup.inc) run
(cube.inc) run

% ------------------------------------------------

[0 0 6 1] set-eye
0 0 -4 translate3d

/floor [0 1 0 2] def

/wd 3 def
/dp 3 def
/fl floor 3 get neg def

/grid {
wd neg 1 wd {
  /i exch def
  i fl dp neg moveto3d
  i fl dp     lineto3d
} for
dp neg 1 dp {
  /i exch def
  wd neg fl i moveto3d
  wd     fl i lineto3d
} for
stroke
} def

page-begin
0 0.5 translate

gsave
0.8 0.8 0.8 setrgbcolor
newpath
grid
grestore

gsave3d
% the shadow
gsave
0.6 0.6 0.6 setrgbcolor

floor light-source plane-project

[1 1 1] A rotate3d
-0.5 -0.5 -0.5 translate3d

cube {
  % [ [P[0] P[1] ... P[n-1]] n ]
  0 get /f exch def
  /ell f length def
  newpath
  f ell 1 sub get 
  aload pop moveto3d
  f {
    aload pop lineto3d
  } forall
  fill
  
} forall

grestore
grestore3d

gsave3d

[1 1 1] A rotate3d
-0.5 -0.5 -0.5 translate3d
/E get-virtual-eye def
/L get-virtual-light def

cube {
  % [ [P[0] P[1] ... P[n-1]] n ]
  dup 
  0 get /f exch def
  1 get /n exch def
  % n = normal function
  /ell f length def
    n E dot-product 
  0 ge 
  {
    newpath
    f ell 1 sub get aload pop moveto3d
    f {
      aload pop lineto3d
    } forall
    gsave
      n L dot-product
    [0.30 0.30 0.80 1] 
    shade 0 0 setrgbcolor
    fill
    grestore
    stroke
  } if
} forall

grestore3d

page-end