求任意两线交点
我用Line方法编了一个画线的程序，不是直线的，现在要求任意两线交点，怎么编这个程序？
[解决办法]
数学都忘光了，翻书看了大半天，弄了一个好象是对的，思路就是解方程，然后判断这样吧：
Option Explicit
Private Type Point
X As Double
Y As Double
End Type
Private Type Lines
P1 As Point
P2 As Point
End Type
Const CROSS As Long = 0 '相交
Const COLINE As Long = 1 '共线
Const PARALLEL As Long = 2 '平行
Private Function GetPoint(L1 As Lines, L2 As Lines, P As Point) As Long
Dim A1 As Double, B1 As Double, C1 As Double
Dim A2 As Double, B2 As Double, C2 As Double
Dim D As Double, R As Double
A1 = L1.P2.Y - L1.P1.Y
B1 = L1.P1.X - L1.P2.X
C1 = L1.P2.X * L1.P1.Y - L1.P1.X * L1.P2.Y
A2 = L2.P2.Y - L2.P1.Y
B2 = L2.P1.X - L2.P2.X
C2 = L2.P2.X * L2.P1.Y - L2.P1.X * L2.P2.Y
D = A2 * B1 - A1 * B2
'Debug.Print A1; B1; A2; B2; C1; C2
If D = 0 Then
If (A1 = A2) And (B1 = B2) Then
GetPoint = COLINE
Else
GetPoint = PARALLEL
End If
Else
P.X = (C1 * B2 - C2 * B1) / D
P.Y = (A1 * C2 - A2 * C1) / D
GetPoint = CROSS
End If
End Function
'测试
Private Sub Command1_Click()
Dim L1 As Lines, L2 As Lines
Dim Pot As Point
Dim R As Long
With L1
.P1.X = -10
.P1.Y = -10
.P2.X = 20
.P2.Y = 20
End With
With L2
.P1.X = 10
.P1.Y = 10
.P2.X = -20
.P2.Y = 20
End With
'PLine L1
'PLine L2
R = GetPoint(L1, L2, Pot)
If R = CROSS Then
MsgBox "X: " & Pot.X & " Y: " & Pot.Y
Else
MsgBox Choose(R, "共线", "平行")
End If
End Sub
