cad中精准抛物线画法

1、1.先用直线命令画一直线(图 1)0过程如下:命令:LINE指定第一点：0,0指定下一点或放弃(U): 'cal>> 表达式：+100*100/200<-30(43.3013 -25.0 0.0)指定下一点或放弃(U):/2.移动该直线，如图24电脑报3授权天徳软$3.用多段线命令画多段线，先向-60度方向拉出适当长度，如图34.继续画多段线，完成一个直角三角形，如图45。过程如下:5. 用REVOLVE命令旋转直角三角形，生成一个三维实体，如图命令：REVOLVE当前线框密度：ISOLINES=4选择对象：(选择直角三角形)选择对象：/指定旋转轴的起点或定义轴依照对

2、象(O)/X 轴(X)/Y 轴(Y):(捕捉A点)指定轴端点：(捕捉B点)指定旋转角度360：/6. 用SECTION命令切割三维实体，生成一个面域，如图6。过程如下：命令：SECTION选择对象：(选择上一步生成的旋转实体)选择对象：/指定截面上的第一个点，依照对象(O)亿 轴(Z)/视图(V)/XY 平面(XY)/YZ 平面(YZ)/ZX 平面(ZX)/三点(3) < 三点>:yz指定YZ 平面上的点<0,0,0>:(捕捉C点)7. 用rotate3d 命令对上一步生成的面域进行三维旋转，如图7。过程如下：命令：rotate3d当前正向角度：ANGDIR= 逆时针

3、ANGBASE=O选择对象：(选择上一步生成的面域)选择对象：/指定轴上的第一个点或定义轴依据对象(0)/最近的(L)/视图(V)/X 轴(X)/Y 轴(Y)亿 轴(Z)/两点(2):(捕捉C点)指定轴上的第二点：(捕捉D点)指定旋转角度或参照(R)： 908.先用EXPLODE命令分解旋转后的面域， 再清理图面，删除不需要的图元，如图8。9.移动抛物线，如图9。完毕!http:/bbs.icax.c n/register.phpSub trparabola ()Dim bq1 , bq2, pt1 , pt2 As VariantDoubleDim aa , ll , yy, a1, a2,

4、 a3, a4, aa1, pt3 (0 To 2 ), bq4( 0 To 2 ) AsDim bq3 (0 To 2 ) As DoubleDim ae As DoubleDim pt33 ( 0 To 2 ) As DoubleDim ptarr (0 To 7 ) As DoubleDim alt As VariantDim objboltb As Acad3DSolidDim al As Varia ntDim lens As AcadLWPolyli ne'求个控制点抛物线顶点:")输入二次项系数：")输入开口弦长：")bq1 = ThisDr

5、awi ng.Utility.GetPoi nt(," aa = ThisDrawi ng.Utility.GetReal("ll = ThisDrawing.Utility.GetDistance(,"aa1 = 1 / aayy = aa * (ll / 2) A 2al = ThisDrawi ng.Utility.A ngleToReal(-30, acDegrees) a2 = ThisDrawing.Utility.AngleToReal(30, acDegrees) a3 = ThisDraw in g.Utility.A ngleToReal(90

6、, acDegrees) a4 = ThisDrawi ng.Utility.A ngleToReal(150, acDegrees) bq2 = ThisDrawi ng.Utility.PolarPoi nt(bq1, a2, yy) pt1 = ThisDrawing.Utility.PolarPoint(bq1, a4, aa1) pt2 = ThisDrawing.Utility.PolarPoint(bq2, a3, aa1) pt3(0) = pt2(0): pt3(1) = pt1(1): pt3(2) = pt1(2) bq3(0) = bq2(0): bq3(1) = bq

7、2(1): bq3(2) = bq2(2) + 10 bq4(0) = bq2(0): bq4(1) = bq1(1): bq4(2) = bq1(2) pt33(0) = 10: pt33(1) = 0: pt33(2) = 0ptarr(0) = pt1(0)ptarr(1) = pt1(1)ptarr(2) = pt2(0)ptarr(3) = pt2(1)ptarr(4) = pt3(0)ptarr(5) = pt3(1)ptarr(6) = pt1(0)ptarr(7) = pt1(1)'画多段线Set lens = ThisDrawing . ModelSpace. Add

8、LightWeightPolyline ( ptarr )Dim objlist (0) As AcadE ntitySet objlist (0) = lens'将多段线变为面域Dim altregi on As AcadRegi onalt = ThisDrawi ng.ModelSpace.AddRegio n(objlist)objlist(0).DeleteSet altregion = alt(0)'旋转面域得到圆锥ae = 2 * Atn (1) *4Set objboltb= ThisDrawing . ModelSpace. AddRevolvedSolid

9、(altregion , pt1 , pt33 , ae)altregion. Delete'切圆锥得到抛物线Set al = objboltb.SectionSolid(bq1, bq2, bq3)objboltb.Deleteal.Rotate bq1, a1al.Rotate3D bq1, bq4, a3Dim explodedobjects As Varia ntexplodedobjects = al.Explodeal.DeleteDim i As In tegerDim ki nd As Stri ngDim parabolaobject As AcadSpli neFor i = 0 To UBou nd(explodedobjects)ki nd = explodedobjects(i).ObjectNameIf ki nd = "AcDbLi ne" The nexplodedobjects(i).DeleteElseSet parabolaobject = explodedobjects(i)End IfNext'旋转抛物线ThisDrawing . SendCommand'rotate"& vbCr & "(Handent ""”&