[编程交流] 弧与多段线弧的角度

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(410 . "Model")
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(10 18.7416 8.43585 0.0)
(40 . 3.50105)
(210 0.0 0.0 1.0)
(100 . "AcDbArc")
(50 . 6.06166)
(51 . 3.36312)

;; Arc to Bulge - Lee Mac 2011
;; cen  - Centre
;; ang1 - Start Angle
;; ang2 - End Angle
;; rad  - Radius
;; Returns: (<vertex> <vertex> <bulge>)
(defun LM:Arc->Bulge ( cen ang1 ang2 rad )
 (list
   (polar cen ang1 rad)
   (polar cen ang2 rad)
   ( (lambda ( a ) (/ (sin a) (cos a))) (/ (rem (+ pi pi (- ang2 ang1)) (+ pi pi)) 4.))
 )
)
;; Bulge to Arc - Lee Mac 2011
;; p1   - Start Vertex
;; p2   - End Vertex
;; bulg - Bulge
;; Returns: (<centre> <start angle> <end angle> <radius>)
(defun LM:Bulge->Arc ( p1 p2 bulg / cen ang rad )
 (setq ang (* 2.0 (atan bulg))
       rad (/ (distance p1 p2) (* 2.0 (sin ang)))
       cen (polar p1 (+ (- (/ pi 2.) ang) (angle p1 p2)) rad)
 )
 (if (minusp bulg)
   (list cen (angle cen p2) (angle cen p1) (abs rad))
   (list cen (angle cen p1) (angle cen p2) (abs rad))
 )
)

;;;;From Cadtutor
;For 90 degrees bulge
;tangent (90/4) = 0.4142 (+/-)
;(tan (/ (* pi 0.5) 4))
;Wizman
(defun Tan (X)
(if (zerop (cos X))
(prompt "Tangent error.")
(/ (sin X) (cos X))))
;Gile
(defun tan (a) (/ (sin a) (cos a)))
; AutoLISP function to convert from Polyline "Bulge" representation
; of an arc to AutoCAD's normal "center, radius, start/end angles"
; form of arc.  This function applies the bulge between two adjacent
; vertices.  It assumes that global symbols "sp", "ep", and "bulge"
; contain the current vertex (start point), next vertex (end point),
; and bulge, respectively.  It sets the appropriate values in global
; symbols "cen", "rad", "sa", and "ea".
; by Duff Kurland - Autodesk, Inc.
; July 7, 1986
(defun cvtbulge (/ cotbce x1 x2 y1 y2 temp)
 (setq x1 (car  sp) x2 (car  ep))
 (setq y1 (cadr sp) y2 (cadr ep))
 (setq cotbce (/ (- (/ 1.0 bulge) bulge) 2.0))
 ; Compute center point and radius
 (setq cen (list (/ (+ x1 x2 (- (* (- y2 y1) cotbce))) 2.0)
                 (/ (+ y1 y2    (* (- x2 x1) cotbce) ) 2.0))
 )
 (setq rad (distance cen sp))
 ; Compute start and end angles
 (setq sa  (atan (- y1 (cadr cen)) (- x1 (car cen))))
 (setq ea  (atan (- y2 (cadr cen)) (- x2 (car cen))))
 (if (< sa 0.0)                      ; Eliminate negative angles
    (setq sa (+ sa (* 2.0 pi)))
 )
 (if (< ea 0.0)
    (setq ea (+ ea (* 2.0 pi)))
 )
 (if (< bulge 0.0)                   ; Swap angles if clockwise
    (progn
       (setq temp sa)
       (setq sa ea)
       (setq ea temp)
    )
 )
)