AutoLISP里getpoint命令如果指定第二個(gè)參數(shù)的話，自動(dòng)實(shí)現(xiàn)橡皮筋效果，但是同時(shí)繪制三條直線的時(shí)候無(wú)法實(shí)現(xiàn)橡皮筋效果，雖然grread函數(shù)能夠?qū)崿F(xiàn)鼠標(biāo)移動(dòng)時(shí)候的預(yù)覽，但是grread函數(shù)執(zhí)行的時(shí)候是不能執(zhí)行對(duì)象捕捉的，因此無(wú)法指定繪圖的第二點(diǎn)。

(defun c:tt ()
    (setq r (getreal "n請(qǐng)輸入管道寬度："))
    (if    (= nil r)
    (setq r 100)
    )
;;;    (If    (= p1 nil)
    (setq p1 (getpoint "n起點(diǎn)："))
;;;    )
    (setq flag t)
    (while (and flag (setq get (grread 1 7 0)))
    (cond
;;;        點(diǎn)擊鼠標(biāo)左鍵畫圖
        ((= 3 (car get))
         (setq p2 (cadr (grread 1)))
         (setq ang (angle p1 p2))
         (setq p1down (polar p1 (+ ang (* 1.5 pi)) (/ r 2)))
         (setq p2down (polar P2 (+ ang (* 1.5 pi)) (/ r 2)))
         (setq p1up (polar p1 (+ ang (/ pi 2)) (/ r 2)))
         (setq p2up (polar p2 (+ ang (/ pi 2)) (/ r 2)))
         (command "line" p1 p2 "")
         (command "line" p1up p2up "")
         (command "line" p1down p2down "")
         (redraw)
         (exit)
        )
;;;        鼠標(biāo)右鍵退出
        ((= 25 (car get))
         (setq flag nil)
        )
;;;        鼠標(biāo)拖動(dòng)顯示預(yù)覽
        ((= 5 (car get))
        
         (setq temppt (list    (car (cadr (grread 1)))
                (cadr (cadr (grread 1)))
              )
         )
         (setq tempang (angle p1 temppt))
         (setq tempp1down (polar p1 (+ tempang (* 1.5 pi)) (/ r 2)))
         (setq
         tempp2down
            (polar temppt
               (+ tempang (* 1.5 pi))
               (/ r 2)
            )
         )
         (setq tempp1up (polar p1 (+ tempang (/ pi 2)) (/ r 2)))
         (setq tempp2up (polar temppt (+ tempang (/ pi 2)) (/ r 2)))
         (redraw)
         (grdraw p1 temppt 1)
         (grdraw tempp1down tempp2down 1) #p#分頁(yè)標(biāo)題#e#
         (grdraw tempp1up tempp2up 1)
        )
        (t nil)
    )
    )
)

該段程序還有一個(gè)問(wèn)題是鼠標(biāo)移動(dòng)的時(shí)候執(zhí)行g(shù)rread函數(shù)但是，點(diǎn)擊鼠標(biāo)左鍵指定繪圖第二點(diǎn)的時(shí)候并不能保證鼠標(biāo)移動(dòng)循環(huán)已經(jīng)結(jié)束，因此當(dāng)光標(biāo)沒(méi)有變成十字型時(shí)候，單擊左鍵無(wú)效，試圖用鼠標(biāo)反應(yīng)器解決該問(wèn)題，但是鼠標(biāo)事件只有雙擊和右鍵單擊事件，沒(méi)有鼠標(biāo)移動(dòng)事件。這里還有網(wǎng)上的一個(gè)類似的問(wèn)題。