[编程交流] 需要有关顶点的帮助

(defun getArcInfo (segment / a p1 bulge p2 c c|2 gamma midp p phi r r2 s theta)
 ;; assign variables to values in argument
 (mapcar 'set '(p1 bulge p2) segment)
 ;; find included angle
 ;; remember that bulge is negative if drawn clockwise
 (setq theta (* 4.0 (atan (abs bulge))))
 ;; output included angle
 (princ (strcat "\n Included angle: " (rtos theta)" rad ("(angtos theta 0)" degrees)"))
 ;; find height of the arc
 (setq c (distance p1 p2) s (* (/ c 2.0) (abs bulge)))
 ;; output height of arc
 (princ (strcat "\n Height of arc:  " (rtos s)))
 ;; output chord length
 (princ (strcat "\n Chord length:   " (rtos c)))
 ;; If this function is used without making sure that the segment
 ;; is not simply a line segment (bulge = 0.0), it will produce
 ;; a division-by-zero error in the following. Therefore we want
 ;; to be sure that it doesn't process line segments.
 (cond ((not (equal bulge 0.0 1E-6))
        ;; find radius of arc
        ;; first find half the chord length
        (setq c|2 (/ c 2.0)
              ;; find radius with Pythagoras (used as output)
              r   (/ (+ (expt c|2 2.0) (expt s 2.0)) (* s 2.0))
              ;; find radius with trigonometry
              r2  (/ c|2 (sin (/ theta 2.0)))
        )
        (princ (strcat "\n Radius of arc:  " (rtos r)))
        ;; find center point of arc with angle arithmetic
        ;; (used as output)
        (setq gamma (/ (- pi theta) 2.0)
              phi   (if (>= bulge 0)
                      (+ (angle p1 p2) gamma)
                      (- (angle p1 p2) gamma)
                    )
              p     (polar p1 phi r)
        )
        ;; find center point of arc with Pythagoras
        (setq a    (sqrt (- (expt r 2.0) (expt c|2 2.0)))
              midp (polar p1 (angle p1 p2) c|2)
              p2   (if (>= bulge 0)
                     (polar midp (+ (angle p1 p2) (/ pi 2.0)) a)
                     (polar midp (- (angle p1 p2) (/ pi 2.0)) a)
                   )
        )
        ;; output coordinates of center point
        (princ (strcat "\n Center of arc:  "(rtos (car p))","(rtos (cadr p))))
       )
       (T (princ "\n Segment has no arc info"))
 )
 (princ)
)
(defun c:POLYARCS (/ a polysegs seg)
 ;; make a list of polyline segments of a
 ;; selected polyline
 (cond ((setq polysegs (getPolySegs))
        ;; a is just an informative counter
        (setq a 0)
                ;; run thru each segment
        (foreach seg polysegs
          (setq a (1+ a))
                  ;; only process the segment if it's an arc
                  ;; i.e. bulge /= 0.0
          (cond ((not (zerop (cadr seg)))
                 (princ (strcat "\nSegment " (itoa a) ": "))
                                        ;;
                 (getArcInfo seg)
                )
          )
        )
       )
 )
)