圆弧取点问题

流_星

(while
         (= nil
          (setq pnt1 (getpoint "\nPick point to place angle: "))
         )
          (alert "\nPlease pick a point")
        )
（setq a 40 b 40 c 5）
        (setq r c)
     (setq d (/ c 2))
     (setq e (/ a 2))
     (setq f (/ b 2))
     (setq r1 (sqrt (/ (expt r 2) 2)))
     (setq r2 (sqrt (/ (expt d 2) 2)))
     (setq pnt2 (list (+(car pnt1)f) (-(cadr pnt1)e) (caddr pnt1)))
     (setq pnt3 (list (+(car pnt1)f) (+(cadr pnt1)e) (caddr pnt1)))
     (setq pnt4 (list (-(+(car pnt1)f)d) (+(cadr pnt1)e) (caddr pnt1)))
     (setq pnt5 (list (-(-(+(car pnt1)f)d)r2) (+(-(+(cadr pnt1)e)d)r2) (caddr pnt1)))
     (setq pnt6 (list (-(+(car pnt1)f)c) (-(+(cadr pnt1)e)d) (caddr pnt1)))
     (setq pnt7 (list (-(+(car pnt1)f)c) (+(+(-(cadr pnt1)e)c)r)(caddr pnt1)))
     (setq pnt8 (list (+(-(-(+(car pnt1)f)c)r)r1)(-(+(+(-(cadr pnt1)e)c)r)r1)(caddr pnt1)))
     (setq pnt9 (list (-(-(+(car pnt1)f)c)r) (+(-(cadr pnt1)e)c) (caddr pnt1)))
     (setq pnt10 (list (+(-(car pnt1)f)d) (+(-(cadr pnt1)e)c) (caddr pnt1)))
     (setq pnt11 (list (-(+(-(car pnt1)f)d)r2)(+(+(-(cadr pnt1)e)d)r2)(caddr pnt1)))
     (setq pnt12 (list (-(car pnt1)f) (+(-(cadr pnt1)e)d) (caddr pnt1)))
     (setq pnt13 (list (-(car pnt1)f) (-(cadr pnt1)e) (caddr pnt1)))
     (setvar "osmode" 0)
     (command "._pline" pnt2 pnt3 pnt4 "_a" "_s" pnt5 pnt6 "_l" pnt7 "_a" "_s" pnt8 pnt9 "_l" pnt10
      "_a" "_s" pnt11 pnt12 "_l" pnt13 "_c")

这是一段画角钢的程序，是老外的

请教大家，r1，r2，与PNT5点，Pnt8点，PNt11点，啥关系，原来是啥
我想了半天没有想明白，请高手指点一下

ZZXXQQ

r1,r2是用沟股定理计算的圆弧中间点坐标值（半径/根号2）
pnt5,pnt8,pnt11是圆弧中间点。
下面是压缩过的程序：

2. (defun c:tt ()
   
3. (while (= nil (setq pt1 (getpoint "\nPick point to place angle: ")))
   
4. (alert "\nPlease pick a point")
   
5. )
   
6. (setq a 40.0 b 40.0 c 5.0)
   
7. (setq r c)
   
8. (setq d (/ c 2))
   
9. (setq e (/ a 2))
   
10. (setq f (/ b 2))
    
11. (setq x (car pt1) y (cadr pt1) z (caddr pt1))
    
12. (setq r1 (sqrt (/ (expt r 2) 2)))
    
13. (setq r2 (sqrt (/ (expt d 2) 2)))
    
14. (setq pt2 (list (+ x f) (- y e) z))
    
15. (setq pt3 (list (+ x f) (+ y e) z))
    
16. (setq pt4 (list (-(+ x f)d) (+ y e) z))
    
17. (setq pt5 (list (-(+ x f)d r2) (-(+ y e r2)d) z))
    
18. (setq pt6 (list (-(+ x f)c) (-(+ y e)d) z))
    
19. (setq pt7 (list (-(+ x f)c) (+(- y e)c r) z))
    
20. (setq pt8 (list (-(+ x f r1)c r) (+(- y e r1)c r) z))
    
21. (setq pt9 (list (-(+ x f)c r) (+(- y e)c) z))
    
22. (setq pt10 (list (+(- x f)d) (+(- y e)c) z))
    
23. (setq pt11 (list (+(- x f r2)d) (+(- y e)d r2) z))
    
24. (setq pt12 (list (- x f) (+(- y e)d) z))
    
25. (setq pt13 (list (- x f) (- y e) z)))
    
26. (setvar "osmode" 0)
    
27. (command "._pline" pt2 pt3 pt4 "_a" "_s" pt5 pt6 "_l" pt7 "_a" "_s" pt8 pt9 "_l" pt10
    
28.       "_a" "_s" pt11 pt12 "_l" pt13 "_c")
    
29. (princ)
    
30. )
    

(defun c:tt ()<br /> (while (= nil (setq pt1 (getpoint "\nPick point to place angle: ")))<br /> (alert "\nPlease pick a point")<br /> )<br /> (setq a 40.0 b 40.0 c 5.0)<br /> (setq r c)<br /> (setq d (/ c 2))<br /> (setq e (/ a 2))<br /> (setq f (/ b 2))<br /> (setq x (car pt1) y (cadr pt1) z (caddr pt1))<br /> (setq r1 (sqrt (/ (expt r 2) 2)))<br /> (setq r2 (sqrt (/ (expt d 2) 2)))<br /> (setq pt2 (list (+ x f) (- y e) z))<br /> (setq pt3 (list (+ x f) (+ y e) z))<br /> (setq pt4 (list (-(+ x f)d) (+ y e) z))<br /> (setq pt5 (list (-(+ x f)d r2) (-(+ y e r2)d) z))<br /> (setq pt6 (list (-(+ x f)c) (-(+ y e)d) z))<br /> (setq pt7 (list (-(+ x f)c) (+(- y e)c r) z))<br /> (setq pt8 (list (-(+ x f r1)c r) (+(- y e r1)c r) z))<br /> (setq pt9 (list (-(+ x f)c r) (+(- y e)c) z))<br /> (setq pt10 (list (+(- x f)d) (+(- y e)c) z))<br /> (setq pt11 (list (+(- x f r2)d) (+(- y e)d r2) z))<br /> (setq pt12 (list (- x f) (+(- y e)d) z))<br /> (setq pt13 (list (- x f) (- y e) z)))<br /> (setvar "osmode" 0)<br /> (command "._pline" pt2 pt3 pt4 "_a" "_s" pt5 pt6 "_l" pt7 "_a" "_s" pt8 pt9 "_l" pt10<br />       "_a" "_s" pt11 pt12 "_l" pt13 "_c")<br /> (princ)<br /> )<br />

还可以这样写：

2. (defun c:tt ()
   
3. (while (= nil (setq pt1 (getpoint "\nPick point to place angle: ")))
   
4. (alert "\nPlease pick a point")
   
5. )
   
6. (setq a 40.0 b 40.0 c 5.0)
   
7. (setq r c)
   
8. (setq d (/ c 2))
   
9. (setq e (/ a 2))
   
10. (setq f (/ b 2))
    
11. (setq x (car pt1) y (cadr pt1) z (caddr pt1))
    
12. (setq r1 (sqrt (/ (expt r 2) 2)))
    
13. (setq r2 (sqrt (/ (expt d 2) 2)))
    
14. (setq pt0 (list (- x f) (- y e) z)))
    
15. (setq pt2 (list (+ x f) (- y e) z))
    
16. (setq pt3 (list (+ x f) (+ y e) z))
    
17. (setq pt4 (list (-(+ x f)d) (+ y e) z))
    
18. (setq pt5 (list (-(+ x f)c) (-(+ y e)d) z))
    
19. (setq pt6 (list (-(+ x f)c) (+(- y e)c r) z))
    
20. (setq pt7 (list (-(+ x f)c r) (+(- y e)c) z))
    
21. (setq pt8 (list (+(- x f)d) (+(- y e)c) z))
    
22. (setq pt9 (list (- x f) (+(- y e)d) z))
    
23. (setvar "osmode" 0)
    
24. (command "._pline" pt2 pt3 pt4 "_a" pt5 "_l" pt6 "_a" pt7 "_l" pt8 "_a" pt9 "_l" pt0 "_c")
    
25. (princ)
    
26. )
    

(defun c:tt ()<br /> (while (= nil (setq pt1 (getpoint "\nPick point to place angle: ")))<br /> (alert "\nPlease pick a point")<br /> )<br /> (setq a 40.0 b 40.0 c 5.0)<br /> (setq r c)<br /> (setq d (/ c 2))<br /> (setq e (/ a 2))<br /> (setq f (/ b 2))<br /> (setq x (car pt1) y (cadr pt1) z (caddr pt1))<br /> (setq r1 (sqrt (/ (expt r 2) 2)))<br /> (setq r2 (sqrt (/ (expt d 2) 2)))<br /> (setq pt0 (list (- x f) (- y e) z)))<br /> (setq pt2 (list (+ x f) (- y e) z)) <br /> (setq pt3 (list (+ x f) (+ y e) z))<br /> (setq pt4 (list (-(+ x f)d) (+ y e) z))<br /> (setq pt5 (list (-(+ x f)c) (-(+ y e)d) z))<br /> (setq pt6 (list (-(+ x f)c) (+(- y e)c r) z))<br /> (setq pt7 (list (-(+ x f)c r) (+(- y e)c) z))<br /> (setq pt8 (list (+(- x f)d) (+(- y e)c) z))<br /> (setq pt9 (list (- x f) (+(- y e)d) z))<br /> (setvar "osmode" 0)<br /> (command "._pline" pt2 pt3 pt4 "_a" pt5 "_l" pt6 "_a" pt7 "_l" pt8 "_a" pt9 "_l" pt0 "_c")<br /> (princ)<br /> )<br />