stl.lisp

(defstruct stl-file header num-points points)
(defstruct stl-point normal point attribs)

(defun read-header (stream)
  (let ((data (make-array 80 :initial-element nil)))
    (read-sequence data stream)
    data))

(defun read-num-triangles (stream)
  (let ((data (make-array 4 :element-type '(unsigned-byte 8))))
    (read-sequence data stream)
    (cl-pack:unpack "l" data)))

(defun read-point (stream)
  (let ((data (make-array (+ (* 4 6) 2) :element-type '(unsigned-byte 8))))
    (read-sequence data stream)
    (multiple-value-bind (nx ny nz px py pz attr) (cl-pack:unpack "ffffffv" data)
      (make-stl-point :normal (list nx ny nz) :point (list px py pz) :attribs attr)
      )))

(defun parse-stl-file (filename)
  (with-open-file (stream filename :element-type '(unsigned-byte 8))
    (let* ((header (read-header stream))
           (ntris (read-num-triangles stream))
           (points (make-array ntris :element-type 'stl-point)))
      (loop for i from 0 to (- ntris 1) do
           (setf (aref points i) (read-point stream)))
      (format t "Header read: ~A~%" header)
      (format t "Number of triangles: ~A~%" ntris)
      (make-stl-file :header header :num-points ntris :points points))))