空间中任意三点，如何转换坐标系使该三点在新坐标系的XY平面内

hanlin369

空间中任意三点，如何转换坐标系使该三点在新坐标系的XY平面内

jkbanana

'给定点p1,p2,p3

Dim p1(0 To 2) As Double

Dim p2(0 To 2) As Double

Dim p3(0 To 2) As Double

''''''''''''''''''''''''''''

''''''''''''''''''''''''''''

Dim vx(0 To 2) As Double

Dim vy(0 To 2) As Double

Dim vz(0 To 2) As Double

Dim x(0 To 2) As Double

Dim y(0 To 2) As Double

Dim z(0 To 2) As Double

Dim i As Integer

'''

'矢量 vx , vy由点p1,p2,p3决定

for i = 0 To 2

  vx(i)=p2(i)-p1(i)

  vy(i)=p3(i)-p1(i)

Next

'UCS坐标系的x轴

for i = 0 To 2

  x(i)=vx(i)

Next

'vz = vx X vy  (矢量的外积运算)

vz(0) = vx(1) * vy(2) - vx(2) * vy(1)

vz(1) = vx(2) * vy(0) - vx(0) * vy(2)

vz(2) = vx(0) * vy(1) - vx(1) * vy(0)

'UCS坐标系的z轴

for i = 0 To 2

  z(i)=vz(i)

Next

'UCS坐标系的y轴  

y(0) = z(1) * x(2) - z(2) * x(1)

y(1) = z(2) * x(0) - z(0) * x(2)

y(2) = z(0) * x(1) - z(1) * x(0)

'则，UCS坐标系

Dim ucsObj As AcadUCS

Dim ucsx(0 To 2) As Double

Dim ucsy(0 To 2) As Double

For i = 0 To 2

  ucsx(i) = p1(i) + x(i)

  ucsy(i) = p1(i) + y(i)

Next

Set ucsObj = ThisDrawing.UserCoordinateSystems.Add(p1, ucsx, ucsy, "UCSName")

hanlin369

我的思路是这样的：

空间中的任意三点p1、p2、p3，一直线L1过p1、p2点，另一条直线L2过p3点与直线L1相垂于p4点，

以p4点为坐标原点，p1(或p2)、P3点分别为x、y轴上的一点，坐标变换。

jkbanana

你的思路很好。

求垂足的方法本论坛也有不少。也不麻烦。