LOGO-L> Filled orange peel

["Tom Lynn" <thl22@cam.ac.uk>]

Hi.

Here's the orange peel again in 3d.  I haven't had time to work on the 
lighting etc., but it's pretty much right.  There's also a glitch at one 
end of the spiral (very clear from the view shown here) and I don't know 
what's causing it, as the wireframe looks ok.  I was very lucky the way the 
red and orange shells separate into an inside and outside so well.

I had a few problems with this one as it uses the towardsxyz command a lot, 
and I don't really understand what controls the roll of the turtle around 
the vector after this command has been used.  This means I don't know what 
state the turtle is left in.

For instance, after a turtle at [0 0 0] does towardsxyz [100 100 100], the 
turtle is pointing along the line [0 0 0]-[100 100 100], but which way do 
its "wings" point?

A useful library procedure (for me, at least) would be copyturtle :n, which 
would set the current turtle in the same position and orientation as turtle 
:n.  Can anyone supply suitable code?

Thanks.

Tom Lynn

to aaa
  cs
  setsc [0 0 0]
  perspective
  setlight [0 0.2] ask -3 [pu setposxyz [100 100 100]]
  rt 150 ; Change this to change orientation of peel

  setpc [255 160 40]
  orangepeel 200 15
  ; Uncomment the rt 180 in the next line to turn it into a ball.
  setpc 4 ;rt 180
  orangepeel 200 15
  wait 100
  polyview
  repeat 72 [ask -1 [fd 200 down 5]]
end

to moveto :pxyz
  setorientation towardsxyz :pxyz
  fd distancexyz :pxyz
end

to orangepeel :radius :strips
; Tracks a spiralling path down around a sphere.

  localmake "v 0
  localmake "r 0
  localmake "hanglestep 7.5
  localmake "vanglestep :hanglestep/:strips
  localmake "stripheight 360*:vanglestep/:hanglestep
  localmake "oldlowerpos [0 0 0]
  localmake "oldnextpos [0 0 0]

  setturtle 0
    localmake "startpos posxyz
    pu fd 10
    localmake "startposmoved posxyz
    bk 10

  setturtle 1
    pu
    setposxyz :startpos
    setorientation towardsxyz :startposmoved

  until [and not (:v < 180) not (:r < 350)] [
    setturtle 1
      pu
      rt :r
      ifelse :v < 180 [up (:v - 90)][up 90]
      fd :radius
      localmake "nextpos posxyz

      if (:v < 180 + :stripheight/2) [
        bk :radius
        ifelse :v > :stripheight/2
          [ifelse :v < 180 [down :stripheight/2][down :stripheight/2-:v+180]]
          [down :v]
        fd :radius
        localmake "lowerpos posxyz
        ask 2 [
          pu setposxyz :lowerpos
          pd polystart
            setposxyz :nextpos
            ifelse :oldnextpos = [0 0 0] [setposxyz :nextpos][setposxyz :oldnextpos]
            ifelse :oldlowerpos = [0 0 0] [setposxyz :nextpos][setposxyz :oldlowerpos]
            setposxyz :lowerpos
          polyend
          make "oldnextpos :nextpos
          make "oldlowerpos :lowerpos
        ]
        bk :radius
        ifelse :v > :stripheight/2
          [ifelse :v < 180 [up :stripheight/2][up :stripheight/2-:v+180]]
          [up :v]
        fd :radius
      ]

      bk :radius
      ifelse :v < 180 [down (:v - 90)][down 90]
      lt :r

    setturtle 0
      pu ; ifelse posxyz = [0 0 0][pu][pd] ; Draw main track
      setposxyz :nextpos

    localmake "r :r + :hanglestep
    if :r > 360 [localmake "r :r - 360]
    localmake "v :v + :vanglestep
  ]

  ; Reset turtle 0 to original state (though it may have rolled a bit...)
  setturtle 0
    pu
    setposxyz :startpos
    setorientation towardsxyz :startposmoved
end
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   ---- File information -----------
     File:  filledpeel.gif
     Date:  26 Jul 1998, 22:34
     Size:  15883 bytes.
     Type:  GIF-image

filledpeel.gif