37 lines
1.1 KiB
Common Lisp
37 lines
1.1 KiB
Common Lisp
;; (require :lispbuilder-sdl)
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(defun deg-to-radian (deg)
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"converts degrees to radians"
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(* deg pi 1/180))
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(defun cos-deg (angle)
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"returns cosin of the angle expressed in degress"
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(cos (deg-to-radian angle)))
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(defun sin-deg (angle)
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"returns sin of the angle expressed in degress"
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(sin (deg-to-radian angle)))
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(defun draw-tree (surface x y angle depth)
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"draws a branch of the tree on the sdl-surface"
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(when (plusp depth)
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(let ((x2 (+ x (round (* depth 10 (cos-deg angle)))))
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(y2 (+ y (round (* depth 10 (sin-deg angle))))))
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(sdl:draw-line-* x y x2 y2 :surface surface :color sdl:*green*)
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(draw-tree surface x2 y2 (- angle 20) (1- depth))
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(draw-tree surface x2 y2 (+ angle 20) (1- depth)))))
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(defun fractal-tree (depth)
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"shows a window with a fractal tree"
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(sdl:with-init ()
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(sdl:window 800 600 :title-caption "fractal-tree")
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(sdl:clear-display sdl:*black*)
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(draw-tree sdl:*default-surface* 400 500 -90 depth)
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(sdl:update-display)
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(sdl:with-events ()
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(:video-expose-event ()
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(sdl:update-display))
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(:quit-event ()
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t))))
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(fractal-tree 9)
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