[求助]求交点！！！

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不在同一个平面的两条直线，怎么才能找到它们的“交点(就是移动到同一平面上的那个交点)”？？，要求：除了把它们移到同一个平面上，还要怎么求？？

zxj_76

把它们的坐标取出来，用数学的方法求！

Orcagna

先把线化成 L1：ax+by=c ; L2：a2x+b2y=c2，
然后套入二元一次线性方程式求解，
求出来的答案，就是它的交点了。
要注意的是，有可能是平行线，
所以在求解之前，要先算一下斜率。

sieben

同3楼的思路,VB6的代码

Function LL_Inter(ByRef List1() As Double, ByVal p1 As Variant, ByVal p2 As Variant, Optional ByVal p3 As Variant, _
                Optional ByVal p4 As Variant) As Variant
   
    Dim Line1(0 To 2) As Double
    Dim Line2(0 To 2) As Double
    If TypeName(p4) = "Error" Then
        If TypeName(p3) = "Error" Then
            Line1(0) = p1(0)
            Line1(1) = p1(1)
            Line1(2) = p1(2)
            Line2(0) = p2(0)
            Line2(1) = p2(1)
            Line2(2) = p2(2)
        Else
            Line_Equation Line1, p1, p2
            Line_Equation Line2, p2, p3
        End If
    Else
        Line_Equation Line1, p1, p2
        Line_Equation Line2, p3, p4
    End If
    Dim dlt As Double
    Dim DltX As Double
    Dim DltY As Double
    dlt = Line1(0) * Line2(1) - Line2(0) * Line1(1)
    DltX = Line1(2) * Line2(1) - Line2(2) * Line1(1)
    DltY = Line1(0) * Line2(2) - Line2(0) - Line1(2)
    If Abs(dlt) < 0.000000001 Then
        If Abs(DltX) < 0.0000001 And Abs(DltY) < 0.0000001 Then
            LL_Inter = -1
        Else
            LL_Inter = -2
        End If
    Else
        LL_Inter = 0
        'List1(0) = -DltX / Dlt
        'List1(1) = -DltY / Dlt
        List1(1) = (Line1(0) * Line2(2) - Line2(0) * Line1(2)) / (Line2(0) * Line1(1) - Line1(0) * Line2(1))
        List1(0) = (Line1(1) * Line2(2) - Line2(1) * Line1(2)) / (Line2(1) * Line1(0) - Line1(1) * Line2(0))
    End If
End Function

Sub Line_Equation(ByRef LParam() As Double, ByVal p1 As Variant, ByVal p2 As Variant)
    LParam(0) = p2(1) - p1(1)
    LParam(1) = p1(0) - p2(0)
    LParam(2) = -1# * LParam(0) * p1(0) - LParam(1) * p1(1)
End Sub

more

非常感谢！

gdzhou

没看懂，，

guodengch

谢谢!..........

he993

假如是无法建立数学方程的曲线qline,和直线zline 相交呢？

vb还又没有办法？

BigJue

请问什么是无法建立数学方程的曲线？规则的曲线都有方程的吧？

如果曲线不规则，怎么知道它的趋势？怎么求交点？