snake.box

An example showing how to use the Line command

To run this example you will need the following file(s): ./snake.box. If the example requires more than one file, then you should put them into the same directory. You can then launch Box with box -l g ./snake.box.

// Under a shell type: box -l g snake.box
// ---
// This example shows the flexibility of the Window.Line instruction, which
// lets you draw lines with variable width: for each point of the line you
// can specify the enter-width and the exit-width. You can also use different
// join styles in the same line. This example shows in particular how to
// define a customized line terminator: predefined line terminators exist
// to draw arrows, but you can also use your own line terminator and draw
// a snake!
include "g"

// Here we draw our line-terminator: this is just a common Window object
// where some hot points have been defined.
eye = Window[][
  Circle[color.yellow, (0, 0), 1, 0.5]
  Circle[color.dark_green, (0, 0), 0.1, 0.5]
]

tongue = Window[][
  Poly[color.dark_red, (0.5, 0), (0.5, 4), 0, 1, (0.5, 5), (1, 5)
       (0, 5), (0, 4.5), (0, 5), (-1, 5), (-0.5, 5), (-0.5, 4)
       0, 0, (-0.5, 0)]
]

// Now we can use the tongue and the eye figures to draw the face of a snake
face = Window[][
  a = Point[(5, -5)], b = Point[(7, 0)]
  c = Point[(4, 8)], d = Point[(0, 9)]
  Poly[color.dark_green, 0.5, a, b, c, d,
       (-c.x, c.y), (-b.x, b.y), (-a.x, a.y)]
  Put[tongue, (0, 6)]
  color.yellow
  Put[eye, (2.6, 0), -70, Scale[1.5]]
  Put[eye, (-2.6, 0), 70, Scale[1.5]]
  color.dark_green

  // These hot points are used by the Window.Line instruction to place
  // the figure at the end of the line.
  // Window.Line behaves as follows:
  //  - it moves the figure such that "head" goes to the final point
  //    of the line;
  //  - it rotates the figure such that the point "tail" is as near
  //    as possible to the second last point of the line;
  //  - it scales the figure such that the distance "tail"-"head" is equal
  //    to the width of the line.
  //  - after the figure has been placed, the line is drawed by connecting
  //    the second last point to the "join" point.
  Hot["head", (0, 9); "tail", (0, 5); "join", (0, -4)]
]

// Now we can draw as many snakes as we want with just one Line instruction!
snake = Window[]
\ snake.Line[color.dark_green, line.smooth, (10, 10), 2, 8, (40, 100), 8, 10
             (80, 10), (120, 90), (150, 25), (170, 55), face, (195, 70)]

snake.Save["snake.png", Window["rgb24", .Res[Dpi[100]]]]