FILL
(FILL fillmode)

Fills in a region of the graphics window containing the turtle and bounded by lines that have been drawn earlier. It fills using the current value of FLOODCOLOR.

If fillmode is TRUE, then it will fill until the current PENCOLOR is encountered. If it is FALSE, then it will fill while on same color.

Fill can be used in PERSPECTIVE mode as long as the area to filled is bounded and you only fill what's in plain view. For example if you have a cube don't draw all 6 faces, only 3 at most can be in view, so draw just those faces and fill them.

; fill a square
REPEAT 4 [FORWARD 100 RIGHT 90]
RIGHT 45
PENUP
FORWARD 20
FILL

; fill while on the same color
SETFLOODCOLOR 4
SETPENCOLOR 1
CIRCLE 50
SETPENCOLOR 2
CIRCLE 100
FILL

; fill until the lines match PENCOLOR
SETFLOODCOLOR 4
SETPENCOLOR 1
CIRCLE 50
SETPENCOLOR 2
CIRCLE 100
(FILL "TRUE)

; A 3D example
TO SQUARE :color
  REPEAT 4 [FORWARD 100 RIGHT 90]
  PENUP
  RIGHT 45
  FORWARD 50
  SETFLOODCOLOR :color
  FILL
  BACK 50
  LEFT 45
  PENDOWN
END

PERSPECTIVE
RIGHTROLL 45
DOWNPITCH 45
SQUARE 1
RIGHTROLL 90
SQUARE 2
UPPITCH 90
SQUARE 3