SolidWorks API Measure类测量点坐标如何显式指定参考坐标系

现有SolidWorks装配体包含基准点P与自定义坐标系F，需求为获取点P相对于坐标系F的X、Y、Z坐标值。初始实现的VB代码如下：

Sub main()
    Dim swApp As SldWorks.SldWorks
    Dim swModel As SldWorks.ModelDoc2
    Dim bstatus As Boolean
    Dim swMeasure As SldWorks.Measure
    
    Set swApp = Application.SldWorks
    Set swModel = swApp.ActiveDoc

    swModel.ClearSelection2 True
    bstatus = swModel.Extension.SelectByID2("P", "DATUMPOINT", 0, 0, 0, False, 0, Nothing, 0)
    Debug.Assert bstatus

    Set swMeasure = swModel.Extension.CreateMeasure
    bstatus = swMeasure.Calculate(Nothing)
    Debug.Assert bstatus

    Debug.Print ("X: " & swMeasure.X)
    Debug.Print ("Y: " & swMeasure.Y)
    Debug.Print ("Z: " & swMeasure.Z)
End Sub

该脚本可正常运行，但输出坐标采用的参考坐标系为软件最近一次激活的坐标系，可能是目标坐标系F也可能是系统默认原点坐标系，结果不可预测。目前未在Measure类的公开接口中找到强制指定参考坐标系的属性，需要确认显式指定测量参考坐标系的方法，或可行的替代解决方案。

IMeasure接口未公开直接设置参考坐标系的属性，不建议依赖该接口的隐式状态获取坐标，最稳定的实现方案是通过SolidWorks的数学变换接口直接做坐标转换，完全不依赖软件界面的历史操作状态，实现步骤如下：

• 分别获取基准点P在系统默认全局坐标系下的坐标值，以及目标坐标系F相对于全局坐标系的变换矩阵
• 对坐标系F的变换矩阵求逆，将点的全局坐标与逆矩阵相乘，得到的结果就是点在F坐标系下的局部坐标

可直接运行的修正代码如下：

Sub main()
    Dim swApp As SldWorks.SldWorks
    Dim swModel As SldWorks.ModelDoc2
    Dim swMathUtil As SldWorks.MathUtility
    Dim bstatus As Boolean
    Dim swPointFeat As SldWorks.Feature
    Dim swPoint As SldWorks.RefPoint
    Dim vPointCoord As Variant
    Dim swMathPoint As SldWorks.MathPoint
    Dim swCoordFeat As SldWorks.Feature
    Dim swCoordSys As SldWorks.CoordinateSystem
    Dim swCoordTransform As SldWorks.MathTransform
    Dim swLocalPoint As SldWorks.MathPoint
    Dim vLocalCoord As Variant
    
    Set swApp = Application.SldWorks
    Set swModel = swApp.ActiveDoc
    Set swMathUtil = swApp.GetMathUtility

    ' 获取基准点P的全局坐标
    swModel.ClearSelection2 True
    bstatus = swModel.Extension.SelectByID2("P", "DATUMPOINT", 0, 0, 0, False, 0, Nothing, 0)
    Debug.Assert bstatus
    Set swPointFeat = swModel.SelectionManager.GetSelectedObject6(1, -1)
    Set swPoint = swPointFeat.GetSpecificFeature2
    vPointCoord = swPoint.GetPoint
    Set swMathPoint = swMathUtil.CreatePoint(vPointCoord)

    ' 获取目标坐标系F的变换矩阵
    swModel.ClearSelection2 True
    bstatus = swModel.Extension.SelectByID2("F", "COORDSYS", 0, 0, 0, False, 0, Nothing, 0)
    Debug.Assert bstatus
    Set swCoordFeat = swModel.SelectionManager.GetSelectedObject6(1, -1)
    Set swCoordSys = swCoordFeat.GetSpecificFeature2
    Set swCoordTransform = swCoordSys.GetTransform
    ' 矩阵求逆，用于全局坐标转F系局部坐标
    Set swCoordTransform = swCoordTransform.Inverse()

    ' 执行坐标变换并输出结果
    Set swLocalPoint = swMathPoint.MultiplyTransform(swCoordTransform)
    vLocalCoord = swLocalPoint.ArrayData
    Debug.Print ("X: " & vLocalCoord(0))
    Debug.Print ("Y: " & vLocalCoord(1))
    Debug.Print ("Z: " & vLocalCoord(2))
End Sub

补充说明：

• 若基准点或目标坐标系位于装配体的子零部件中，需要额外叠加对应零部件的位姿变换矩阵，否则会出现坐标偏差
• 若一定要使用IMeasure接口，可在调用Calculate方法前先选中目标坐标系F将其激活，此时测量结果会以F为参考，但该方法依赖软件内部状态，不同SolidWorks版本表现可能不一致，不建议在正式脚本中使用

内容的提问来源于stack exchange，提问作者Maksim Surov