[求助]如何画椭圆弧
 

[求助]如何画椭圆弧
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[求助]如何画椭圆弧
我要画的是一个椭圆封头，有一个半椭圆的图形，我怎么也画不出来。顺便请教，如何知道command是如何调用cad里面的各种命令啊，有什么规律可循吗？下面是我下的代码，非常感谢！！
(defun c:tt()
(setvar "cmdecho" 0)
(setq b(getreal "请输入封头壁厚："))
(setq cp(getpoint "请选封头中心："))
(setq cp1(getpoint "请选封头中心右边的端点（内壁）："))
(setq r1(distance cp cp1))
(setq r2(+ r1 25))
(setq cp3(polar cp 0 r2))
(setq cp2(polar cp pi r1))
(setq cp4(polar cp pi r2))
(setq cc(polar cp (/ pi 2) 25))
(setq cc1(polar cp1 (/ pi 2) 25))
(setq cc2(polar cp2 (/ pi 2) 25))
(setq cc3(polar cp3 (/ pi 2) 25))
(setq cc4(polar cp4 (/ pi 2) 25))
(setvar "clayer" "2细线层")
(command "line" cp1 cc1 "")
(command "line" cp2 cc2 "")
(command "line" cp3 cc3 "")
(command "line" cp4 cc4 "")
(command "ellipse" a cc2 cc1 r1)
(princ)
)
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( c:tt()
( "cmdecho" 0)
( b( "请输入封头壁厚："))
( cp( "请选封头中心："))
( cp1( "请选封头中心右边的端点（内壁）："))
( r1 ( cp cp1))
( r2 ( r1 b))
( cp3( cp 0 r2))
( cp2( cp pi r1))
( cp4( cp pi r2))
( cc( cp ( pi 2) 25))
( cc1( cp1 ( pi 2) 25))
( cc2( cp2 ( pi 2) 25))
( cc3( cp3 ( pi 2) 25))
( cc4( cp4 ( pi 2) 25))
( "clayer" "2细线层")
( "line" cp1 cc1 "")
( "line" cp2 cc2 "")
( "line" cp3 cc3 "")
( "line" cp4 cc4 "")
( "ellipse" "_a" cc1 cc2 ( r1 2) cc1 cc2)
( "ellipse" "_a" cc3 cc4 ( ( r1 2) b) cc3 cc4)
()
)
踅摸
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zzxx
非常感谢，自己搞了几天没有搞出来，下了，参考
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