[原创][讨论]：[0215]三点求逆时针角度

vken7az2p

写了一个三点求逆时针方向角度
想请讨论一下是否有更方便的计算方法

附上图片及程序

(DEFUN CCW_ANG ( p1 p2 p3 / A B )
(setq A (RTOD (ANGLE P2 P1)))
(setq B (RTOD (ANGLE P2 P3)))
(COND
((AND (> A 180)
      (> A B)
      (< B 180))
(SETQ ANG (+ B (- 360 A) ))
)

((AND (< A 180)
      (< A B)
      (> B 180))
(SETQ ANG (+ (- B 180) (- 180 A) ))
)
((AND (> A 180)
      (> A B)
      (> B 180))
(SETQ ANG (+ B (- 360 A) ))
)
((AND (< A 180)
      (< A B)
      (< B 180))
(SETQ ANG (- B A))
)   
((AND (< A 180)
      (> A B)
      (< B 180))
(SETQ ANG (- A B))
)
((AND (> A 180)
      (< A B)
      (> B 180))
(SETQ ANG (- B A))
)

(T NIL)
)
ANG
)

测试:
(setq p1 (getpoint "\n起点:"))
(setq p2 (getpoint "\n中点:"))
(setq p3 (getpoint "\n终点:"))
(PRINT (CCW_ANG p1 p2 p3))

如:
由点 B R C 则返回 角度100
由点 C R B 则返回 角度260

无痕

不知道可不可以，没仔细想：

3. ;| (acan p1 p2 p3) = 求３点逆时针角度.----by lxx.2007.2
4. 参数: p1 p2 p3 点. p2为角点.
5. 返回:　弧度角.
6. |;
7. (defun acan (p1 p2 p3 / ans a b an)
8.   (setq ans (list(angle p1 p2)(angle p3 p2))
9. a (apply 'min ans)
10. b (apply 'max ans)
11. an (- b a))
12.   (if (= a (car ans))
13.     an
14.     (- (* 2 PI) an)
15.   )
16. )

;| (acan p1 p2 p3) = 求３点逆时针角度.----by lxx.2007.2 参数: p1 p2 p3 点. p2为角点. 返回:　弧度角. |; (defun acan (p1 p2 p3 / ans a b an)   (setq ans (list(angle p1 p2)(angle p3 p2)) a (apply 'min ans) b (apply 'max ans) an (- b a))   (if (= a (car ans))     an     (- (* 2 PI) an)   ) )

测试:

2. (defun c:tt()
3.   (setq p1 (getpoint "1:")
4. p2 (getpoint "2:")
5. p3 (getpoint "3:"))
6.   (* 180(/(acan p1 p2 p3)PI))
7. )

(defun c:tt()   (setq p1 (getpoint "1:") p2 (getpoint "2:") p3 (getpoint "3:"))   (* 180(/(acan p1 p2 p3)PI)) )

aphey

ANG=B-A

IF ANG < 0 THEN ANG = ANG + 360

这一句判断应该就足够了吧 

byghbcx

就是,一句就足够了,一楼的程序实际上就是一个判断,他分别就a<b,a>b的两种情况下分别列出了a<180,b<180;a<180,b>180;a>180,b>180三种情况,但最后的setq还是一样的.

试试

(DEFUN CCW_ANG (/ p1 p2 p3 A B)

  (setvar "cmdecho" 0)
  (setq p1 (getpoint "\n起点:"))
  (setq p2 (getpoint "\n中点:"))
  (setq p3 (getpoint "\n终点:"))
  (setq A (ANGLE P2 P1))
  (setq B (ANGLE P2 P3))
  (command "_.line" p1 p2 p3 "")
  (command "_.arc" "c" p2 (polar p2 A (/ (+ (distance p2 p1) (distance p2 p3)) 10)) (polar p2 B (/ (+ (distance p2 p1) (distance p2 p3)) 10)))
  (COND
    ((> A B)
     (SETQ ANG (+ B (- (* 2 pi) A)))
     )
    ((< A B)
     (SETQ ANG (- B A))
     )
    (T NIL)
    )
  (setq ANG (angtos ang 0))
  (PRINc (strcat "\n三点逆时针角度：" ang "度"))

  (setvar "cmdecho" 1)
)