#@gimp Drop shadow 3d : gimp_drop_shadow3d, gimp_drop_shadow3d_preview(1)
#@gimp : X-angle = float(0,-90,90)
#@gimp : Y-angle = float(0,-90,90)
#@gimp : Z-angle = float(0,-90,90)
#@gimp : Zoom = float(0,-100,100)
#@gimp : X-offset = float(1,-50,50)
#@gimp : Y-offset = float(1,-50,50)
#@gimp : Perspective = float(2,0,10)
#@gimp : Smoothness = float(0.5,0,5)
#@gimp : Color = color(0,0,0,200)
#@gimp : Preview only shadow = bool(0)
#@gimp : sep = separator(), note = note("<small>Author: <i>David Tschumperl&#233;</i>.      Latest update: <i>2013/07/02</i>.</small>")
gimp_drop_shadow3d :
  -repeat @# -l[$<]
    --_gimp_drop_shadow3d $*
  -endl -done

gimp_drop_shadow3d_preview :
  -repeat @# -l[$<]
    -if $13 -_gimp_drop_shadow3d $*
    -else --_gimp_drop_shadow3d $* -blend alpha,1,1
    -endif
  -endl -done

_gimp_drop_shadow3d :
  -point3d 0,0,1 -r3d[-1] 1,0,0,$1 -r3d[-1] 0,1,0,$2 -r3d[-1] 0,0,1,$3
  u={i(0,8)} v={i(0,9)} w={i(0,10)} -rm[-1]
  -to_a -channels 100%
  --f 'X=x/w-0.5;Y=y/h-0.5;A=($7+$4*$7/100)*$w/(X*$u+Y*$v+$7*$w);if(A<0,1e8,A)'
  --*[-1] 'y/h-0.5' -*[-2] 'x/w-0.5' -+[-2] {0.5-$5/100} -+[-1] {0.5-$6/100} -*[-2] {w} -*[-1] {h}
  -a[-2,-1] c -warp[0] [-1],0,1,0 -rm[-1]
  -b $8% -n 0,$12 -i[-2] ($9^$10^$11) -r[-2] [-1],[-1],1,3 -a[-2,-1] c