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;;;; turtle-system.lisp
(in-package #:l-system)
;;;(matrix* translate rotate scale)
(export 'f)
(export 'q)
(export '[)
(export '])
(defun turtle-system (fn list)
(iter (with pos = (sb-cga:vec 0.0 0.0 0.0))
(with vec-x = (sb-cga:vec 1.0 0.0 0.0))
(with vec-y = (sb-cga:vec 0.0 1.0 0.0))
(with vec-z = (sb-cga:vec 0.0 0.0 1.0))
(with stack = '())
(for item in list)
(case (car item)
;;Move forward one unit,adding data to mesh.
((f)
(let ((new-pos
(vec+ pos
(vec* vec-y
(cadr item)))))
(appending (funcall fn pos new-pos vec-x vec-y vec-z))
(setf pos new-pos)))
;;Move forward one unit,without adding data to mesh.
((j)
(setf pos
(vec+ pos
(vec* vec-y
(cadr item)))))
;;Rotate left on axis z
((+)
(setf vec-x (vec-rotate-around vec-x vec-z (cadr item))
vec-y (vec-rotate-around vec-y vec-z (cadr item))))
;;Rotate right on axis z
((-)
(setf vec-x (vec-rotate-around vec-x vec-z (- (cadr item)))
vec-y (vec-rotate-around vec-y vec-z (- (cadr item)))))
;;Rotate left on axis y
((&)
(setf vec-x (vec-rotate-around vec-x vec-y (cadr item))
vec-z (vec-rotate-around vec-z vec-y (cadr item))))
;;Rotate right on axis y
((^)
(setf vec-x (vec-rotate-around vec-x vec-y (- (cadr item)))
vec-z (vec-rotate-around vec-z vec-y (- (cadr item)))))
;;Rotate left on axis x
((q)
(setf vec-z (vec-rotate-around vec-z vec-x (cadr item))
vec-y (vec-rotate-around vec-y vec-x (cadr item))))
;;Rotate right on axis x
((/)
(setf vec-z (vec-rotate-around vec-z vec-x (- (cadr item)))
vec-y (vec-rotate-around vec-y vec-x (- (cadr item)))))
;;Push the current turtle state onto a stack
(([)
(push (list pos vec-x vec-y vec-z)
stack))
;;Pop the turtle stack, restoring an earlier state
((])
(let* ((asd (pop stack)))
(setf pos (pop asd)
vec-x (pop asd)
vec-y (pop asd)
vec-z (pop asd)))))))
;;; Turgle utils
(defun list-of-vectors->list (list-of-vectors)
(iterconcat #'(lambda (vec)
(concatenate 'list
vec))
list-of-vectors))
(defun vec-rotate-around (vec vec-rotation angle)
"Rotate vec around vec-rotation axis by angle"
(transform-point (vec 0.0 0.0 0.0)
(matrix*
(rotate-around vec-rotation angle)
(translate vec))))
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