document some code samples
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Scott Richmond
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ch_2_code.ld
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176
ch_2_code.ld
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&&&&& Code examples from Chapter 2
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&&& Common "library" functions
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fn ngon!
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fn cngon!
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fn arrow!
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fn flash!
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&&& FIGURE 16
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fn pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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total_angle
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n) -> {
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if lt? (n, 1) then cngon! (90, pipe_rad)
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else {
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penup! ()
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forward! (add (pipe_rad, roll_rad))
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pendown! ()
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left! (mult (total_angle, div (pipe_rad, roll_rad)))
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& flash! (flash_len)
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& cngon! (2, roll_rad)
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arrow! (mult (-1.5, roll_rad))
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cngon! (90, roll_rad)
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rt! (mult (total_angle, div (pipe_rad, roll_rad)))
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penup! ()
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back! (add (pipe_rad, roll_rad))
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left! (theta)
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pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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add (total_angle
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theta)
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dec (n))
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}
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}
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pipegon! (60, -30, inv (6), 0, 6)
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&&& FIGURE 17
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fn pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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total_angle
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n) -> {
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if lt? (n, 1) then cngon! (90, pipe_rad)
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else {
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penup! ()
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forward! (add (pipe_rad, roll_rad))
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pendown! ()
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left! (mult (total_angle, div (pipe_rad, roll_rad)))
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& flash! (flash_len)
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& cngon! (2, roll_rad)
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arrow! (mult (-1.5, roll_rad))
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& cngon! (90, roll_rad)
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rt! (mult (total_angle, div (pipe_rad, roll_rad)))
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penup! ()
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back! (add (pipe_rad, roll_rad))
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left! (theta)
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pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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add (total_angle
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theta)
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dec (n))
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}
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}
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pipegon! (60, -30, inv (180), 0, 180)
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&&& FIGURE 18
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fn pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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total_angle
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n) -> {
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if lt? (n, 1) then cngon! (90, pipe_rad)
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else {
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penup! ()
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forward! (add (pipe_rad, roll_rad))
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pendown! ()
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left! (mult (total_angle, div (pipe_rad, roll_rad)))
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& flash! (flash_len)
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cngon! (2, roll_rad)
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& arrow! (mult (-1.5, roll_rad))
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& cngon! (90, roll_rad)
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rt! (mult (total_angle, div (pipe_rad, roll_rad)))
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penup! ()
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back! (add (pipe_rad, roll_rad))
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left! (theta)
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pipegon! (pipe_rad
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roll_rad
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& flash_len
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theta
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add (total_angle
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theta)
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dec (n))
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}
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}
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pipegon! (60, -30, inv (180), 0, 180)
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&&& FIGURE 19
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fn pipegon! (pipe_rad
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roll_rad
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flash_len
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theta
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total_angle
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n) -> {
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if lt? (n, 1) then cngon! (90, pipe_rad)
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else {
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penup! ()
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forward! (add (pipe_rad, roll_rad))
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pendown! ()
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left! (mult (total_angle, div (pipe_rad, roll_rad)))
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flash! (flash_len)
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& cngon! (2, roll_rad)
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& arrow! (mult (-1.5, roll_rad))
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& cngon! (90, roll_rad)
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rt! (mult (total_angle, div (pipe_rad, roll_rad)))
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penup! ()
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back! (add (pipe_rad, roll_rad))
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left! (theta)
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pipegon! (pipe_rad
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roll_rad
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flash_len
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theta
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add (total_angle
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theta)
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dec (n))
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}
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}
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pipegon! (60, -30, 40, inv (180), 0, 180)
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&&& FIGURE 20
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& The mathematics of spirographs
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& The "degree of symmetrey" is the denominator of the
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& most reduced fraction of the ratio of the two circle dimensions
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& And, drawing something internally (as opposed to externally)
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& the star doubles its number of points.
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& To draw a 40-pointed star (which is what is in _VMwL), you need
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& a fraction with a prime number in the numerator and 20 in the
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& denominator.
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& The other determinant of what the pipegon spirograph looks like
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& is the frequency with which you draw your "stripe"
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& I believe the diagrams in the book use 72 iterations/rotation,
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& for 5º per iteration. That's what's below, but there are many
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& I prefer. 45 iterations gives a lovely pentagon in the middle, 100
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& iteration is lovely.
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& the iteration of these below is s_pipegon!
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pipegon! (400, -140, inv (72), 0, mult (1, 72))
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pipegon! (400, -140, inv (72), 0, mult (2, 72))
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pipegon! (400, -140, inv (72), 0, mult (3, 72))
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pipegon! (400, -140, inv (72), 0, mult (4, 72))
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pipegon! (400, -140, inv (72), 0, mult (5, 72))
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pipegon! (400, -140, inv (72), 0, mult (6, 72))
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pipegon! (400, -140, inv (72), 0, mult (7, 72))
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&&& FIGURE 21.1-4: larger roller than pipe, internally
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& Again, all are s_pipegon!s
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& 21.1
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pipegon! (500, -600, inv (72), 0, mult (3, 72))
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& 21.2
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rt! (inv (18)); pipegon! (450, -500, inv (72), 0, mult (5, 72))
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& 21.3
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rt! (0.125); pipegon! (400, -600, inv (72), 0, mult (3, 72))
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& 21.4
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pipegon! (200, -600, inv (72), 0, mult (3, 72))
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