已知一条直线和直线外一点求垂足??

路边

求助:已知一条线两端点坐标(x1,y1);(x2,y2)和直线外一点(x3,y3),用VBA怎样求出垂足????请那位老兄给个代码!!!

wyj7485

提问前先搜索下，有的:

http://www.mjtd.com/BBS/dispbbs.asp?BoardID=4&replyID=61741&id=27865&skin=0

jkbanana

Option Explicit
Public Sub Sample()
  Dim objline As AcadLine
  Dim lineObj As AcadLine
  Dim returnPnt As Variant
  Dim sp(0 To 2) As Double
  Dim ep(0 To 2) As Double
  Dim ang As Double
  Dim pt(0 To 2) As Double
  Const pi = 3.14159

  '1. 一条线两端点坐标(x1,y1);(x2,y2) ：设该直线为objline
  '   如果只有两端点坐标(x1,y1);(x2,y2), 可用 addline 方法画出该直线
  ThisDrawing.Utility.GetEntity objline, pt, "Select a line"
  ang = objline.Angle
  returnPnt = ThisDrawing.Utility.GetPoint(, "Enter a point: ")
  sp(0) = returnPnt(0)
  sp(1) = returnPnt(1)
  sp(2) = returnPnt(2)

  '2.做直线objline的垂线lineObj
  ep(0) = sp(0) + Cos(ang + pi / 2)
  ep(1) = sp(1) + Sin(ang + pi / 2)
  ep(2) = sp(2)
  Set lineObj = ThisDrawing.ModelSpace.AddLine(sp, ep)
 
  '3.找出直线objline和它的垂线lineObj的交点pt
  returnPnt = lineObj.IntersectWith(objline, acExtendNone)
  If VarType(returnPnt) <> vbEmpty Then
     If LBound(returnPnt) <= UBound(returnPnt) Then
        pt(0) = returnPnt(0)
        pt(1) = returnPnt(1)
        pt(2) = returnPnt(2)
     End If
  End If
  returnPnt = lineObj.IntersectWith(objline, acExtendBoth)
  If VarType(returnPnt) <> vbEmpty Then
     If LBound(returnPnt) <= UBound(returnPnt) Then
        pt(0) = returnPnt(0)
        pt(1) = returnPnt(1)
        pt(2) = returnPnt(2)
     End If
  End If
  lineObj.Delete
 
  '4.画垂线
  Dim obj1 As AcadLine
  Set obj1 = ThisDrawing.ModelSpace.AddLine(sp, pt)
End Sub

兰州人

如何是空间任意直线,你这种就有局限了.你这个公式是解决X-Y平面的.

我不会3X3矩阵的展开式.你能将下列成

X=??

Y= ??

Z = ??

形体的旋转变换有绕主轴旋转，或绕空间任一直线旋转等多种形式。若令Rθ表示绕z轴转θ角，Rβ表示绕y轴转β角，Rγ表示绕x轴转γ角，则点P绕x、y、z轴转γ、β、θ角的变换公式是
Ｒ＝RθRβRγ
     |  cosθ   sinθ   0 |
Rθ＝ | -sinθ   cosθ    0  |
      |  0       0     1  |

     |  cosβ  -sinβ   0  |
Rβ＝ |   0     1     0   |
     |  sinβ  cosβ    1   |

     |  1     0       0   |
Rγ＝ |  0    cosγ   sinγ  |
     |  0     -sinγ  cosγ |

biztech

三楼的函数有问题吧,

ep(0) = sp(0) + Cos(ang + pi / 2)
ep(1) = sp(1) + Sin(ang + pi / 2)

这部分没有乘上垂线长度.