VBA 中Rotate3D 的应用

在三维旋转的时候  我们很难找到旋转轴 也很难确定 我们要旋转的空间 角度。我通过旋转对象的轴线和 旋转方向上的一条直线，找到旋转平面，然后计算这个平面的法线方程。再计算两条直线的夹角，在平面内旋转这个角度就到了。三维旋转轴就是平面的法线，旋转的角度就是两条直线的夹角。

Sub Rotate3D_1()
    On Error Resume Next
    Dim Obj As AcadEntity
    Dim PickPnt
    Dim A As Double, B As Double, C As Double, D As Double
    Dim P1 As Variant, P2 As Variant, P3 As Variant
    Dim T(0 To 2) As Double
    Dim L1 As Double, L2 As Double, L3 As Double
    Dim J As Double
    ThisDrawing.Utility.GetEntity Obj, PickPnt, "选择旋转对象："
    ThisDrawing.Utility.InitializeUserInput 1, ""
    P1 = ThisDrawing.Utility.GetPoint(, "旋转对象轴线上一点:")
    ThisDrawing.Utility.InitializeUserInput 1, ""
    P2 = ThisDrawing.Utility.GetPoint(, "旋转对象轴线与旋转方向直线的交点:")
    ThisDrawing.Utility.InitializeUserInput 1, ""
    P3 = ThisDrawing.Utility.GetPoint(, "旋转方向直线上的另一点:")
   
    KJPMFC P1, P2, P3, A, B, C, D
    MsgBox A
    '过平面法线的一点
    T(0) = A * 10 + P2(0)
    T(1) = B * 10 + P2(1)
    T(2) = C * 10 + P2(2)
    '计算空间两条直线的夹角
    L1 = P2PDistance(P1, P2)
    L2 = P2PDistance(P2, P3)
    L3 = P2PDistance(P3, P1)
           
    '利用余弦定理 a^2=b^2+c^2-2*b*c*cos(A)
           
    J = Arccos((L1 * L1 + L2 * L2 - L3 * L3) / 2 / L1 / L2)
   
    Obj.Rotate3d P2, T, -J

End Sub