VB.NET 中正确使用GetExistingFacets

最近看到论坛中一个很有用的问题，谈到如何正确使用GetExistingFacets。原文地址

http://forums.autodesk.com/t5/Autodesk-Inventor-Customization/GetExistingFacets-VBA-7-and-VB-NET-showsdifferent-and-fails-in/m-p/4314682/highlight/true#M44716

简述如下：

API帮助文档的例子ZHeightColors是用VBA写的，它首先通过GetExistingFacets获取当前实体的面片信息，基于此构造Client Graphics，然后沿着实体的包围盒Z方向，最小值位置设置为红色，最高值设置为蓝色，期间的颜色为渐变色。

VBA

Public Sub ZHeightColors()
    ' Get the surface body from the active document.
    Dim oPartDoc As PartDocument
    Set oPartDoc = ThisApplication.ActiveDocument
    Dim oSurfBody As SurfaceBody
    Set oSurfBody = oPartDoc.ComponentDefinition.SurfaceBodies.Item(1)
    Set oSurfBody = oPartDoc.ComponentDefinitions.Item(1).SurfaceBodies.Item(1)
 
    ' Delete the graphics data set and client graphics,if they exist.
    Dim oDataSets As GraphicsDataSets
    On Error Resume Next
    Set oDataSets = oPartDoc.GraphicsDataSetsCollection.Item("MyTest")
    If Err.Number = 0 Then
        oDataSets.Delete
        oPartDoc.ComponentDefinition.ClientGraphicsCollection.Item("MyTest").Delete
        oSurfBody.Visible = True
        ThisApplication.ActiveView.Update
        Exit Sub
    End If
    On Error GoTo 0
    
    ' Determine the highest tolerance of the existing facet sets.
    Dim ToleranceCount As Long
    Dim ExistingTolerances() As Double
    Call oSurfBody.GetExistingFacetTolerances(ToleranceCount,ExistingTolerances)
    
    Dim i As Long
    Dim BestTolerance As Double
    For i = 0 To ToleranceCount - 1
        If i = 0 Then
            BestTolerance = ExistingTolerances(i)
        ElseIf ExistingTolerances(i) < BestTolerance Then
            BestTolerance = ExistingTolerances(i)
        End If
    Next
    
    ' Get a set of existing facets.
    Dim iVertexCount As Long
    Dim iFacetCount As Long
    Dim adVertexCoords() As Double
    Dim adNormalVectors() As Double
    Dim aiVertexIndices() As Long
    Call oSurfBody.GetExistingFacets(BestTolerance,iVertexCount,iFacetCount,_
                                    adVertexCoords,adNormalVectors,aiVertexIndices)
                                                   
    ' Start a transaction.
    Dim oTrans As Transaction
    Set oTrans = ThisApplication.TransactionManager.StartTransaction(oPartDoc,"Z Height Colors")
 
    ' Create the graphics data sets collection.
    Set oDataSets = oPartDoc.GraphicsDataSetsCollection.Add("MyTest")
    
    ' Create the coordinate set and set it using the coordinates from the facets.
    Dim oGraphicsCoordSet As GraphicsCoordinateSet
    Set oGraphicsCoordSet = oDataSets.CreateCoordinateSet(1)
    Call oGraphicsCoordSet.PutCoordinates(adVertexCoords)
    
    ' Create the index set and set it using the indices from the facets.
    Dim oGraphicsIndexSet As GraphicsIndexSet
    Set oGraphicsIndexSet = oDataSets.CreateIndexSet(2)
    Call oGraphicsIndexSet.PutIndices(aiVertexIndices)
    
    ' Create the normal set and set it using the normals from the facets.
    Dim oGraphicsNormalSet As GraphicsNormalSet
    Set oGraphicsNormalSet = oDataSets.CreateNormalSet(3)
    Call oGraphicsNormalSet.PutNormals(adNormalVectors)
    
    ' Determine the min-max range of the body in Z.
    Dim dMinZ As Double
    dMinZ = oSurfBody.RangeBox.MinPoint.Z
    Dim dMaxZ As Double
    dMaxZ = oSurfBody.RangeBox.MaxPoint.Z
    Dim dHeightDifference As Double
    dHeightDifference = dMaxZ - dMinZ
    
    ' Allocate the array that will contain the color information.
    ' This array contains RGB values for each vertex.
    Dim abtColors() As Byte
    ReDim abtColors(0 To iVertexCount * 3 - 1) As Byte
    
    ' Load the array with color information for each vertex.
    For i = 0 To iVertexCount - 1
        ' Get the Z height of the current vertex.
        Dim dZValue As Double
        dZValue = adVertexCoords(i * 3 + 2)
        
        ' Set the color information for the current vertex.  It's computed by
        ' determining the percentage of the total Z range of the body this vertex
        ' is within.  A color between red and blue is computed based on this percentage.
        ' Blue is at the minimum Z and Red is at the maximum Z with blending between.
        abtColors(i * 3) = ((dZValue - dMinZ) / dHeightDifference) * 255
        abtColors(i * 3 + 1) = 0
        abtColors(i * 3 + 2) = ((dMaxZ - dZValue) / dHeightDifference) * 255
    Next
    
    ' Create the color set and set it using the array of rgb values just created.
    Dim oGraphicsColorSet As GraphicsColorSet
    Set oGraphicsColorSet = oDataSets.CreateColorSet(4)
    Call oGraphicsColorSet.PutColors(abtColors)
 
    ' Create the client graphics collection.
    Dim oClientGraphics As ClientGraphics
    Set oClientGraphics = oPartDoc.ComponentDefinition.ClientGraphicsCollection.Add("MyTest")
    
    ' Create a graphics node.
    Dim oGraphicNode As GraphicsNode
    Set oGraphicNode = oClientGraphics.AddNode(1)
    
    ' Create the triangle graphics.
    Dim oTriangles As TriangleGraphics
    Set oTriangles = oGraphicNode.AddTriangleGraphics
    
    ' Set varIoUs prroperties of the triangle graphics.
    oTriangles.CoordinateSet = oGraphicsCoordSet
    oTriangles.CoordinateIndexSet = oGraphicsIndexSet
    oTriangles.NormalSet = oGraphicsNormalSet
    oTriangles.NormalBinding = kPerVertexNormals
    oTriangles.NormalIndexSet = oGraphicsIndexSet
    oTriangles.ColorSet = oGraphicsColorSet
    oTriangles.ColorBinding = kPerVertexColors
    oTriangles.ColorIndexSet = oGraphicsIndexSet
 
    ' Turn off the display of the body.
    oSurfBody.Visible = False
    
    ' End the transaction.
    oTrans.End
 
    ' Update the view.
    ThisApplication.ActiveView.Update
End Sub

将此段代码贴到VB.NET，调整一些语法错误，编译通过。运行会发现GetExistingFacets 失败。这是为什么呢？

1. 首先是在.NET 中定义COM的整型数组，需要用Integers. MSDN是这样说的

If you are interfacing with components not written for the .NET Framework,for example Automation or COM objects,keep in mind that Long has a different data width (32 bits) in other environments. If you are passing a 32-bit argument to such a component,declare it as Integer instead of Long in your new Visual Basic code.

2. 注意数组以0为起始序号，而很多VBA的数组定义为：

Dim stuff(1 to 10) As Double

3. VB.NET中需要对数组初始化，而不能只是定义。例如

Dim adVertexCoords() As Double

需要变成

Dim adVertexCoords() As Double = {}

基于这些注意事项，以上的VBA代码修改如下后，就能成功运行了。

VB.NET

    Public Sub ZHeightColors()
        ' Get the surface body from the active document.
        Dim oPartDoc As PartDocument
        oPartDoc = m_invApp.ActiveDocument
        Dim oSurfBody As SurfaceBody
        oSurfBody = oPartDoc.ComponentDefinition.SurfaceBodies.Item(1)
        oSurfBody = oPartDoc.ComponentDefinitions.Item(1).SurfaceBodies.Item(1)
 
        ' Delete the graphics data set and client graphics,if they exist.
        Dim oDataSets As GraphicsDataSets
        On Error Resume Next
        oDataSets = oPartDoc.GraphicsDataSetsCollection.Item("MyTest")
        If Err.Number = 0 Then
            oDataSets.Delete()
            oPartDoc.ComponentDefinition.ClientGraphicsCollection.Item("MyTest").Delete()
            oSurfBody.Visible = True
            m_invApp.ActiveView.Update()
            Exit Sub
        End If
        On Error GoTo 0
 
        ' Determine the highest tolerance of the existing facet sets.
        Dim ToleranceCount As Integer
        Dim ExistingTolerances() As Double = {}
        Call oSurfBody.GetExistingFacetTolerances(ToleranceCount,ExistingTolerances)
 
        Dim i As Integer
        Dim BestTolerance As Double
        For i = 0 To ToleranceCount - 1
            If i = 0 Then
                BestTolerance = ExistingTolerances(i)
            ElseIf ExistingTolerances(i) < BestTolerance Then
                BestTolerance = ExistingTolerances(i)
            End If
        Next
 
        ' Get a set of existing facets.
        Dim iVertexCount As Integer
        Dim iFacetCount As Integer
        Dim adVertexCoords() As Double = {}
        Dim adNormalVectors() As Double = {}
        Dim aiVertexIndices() As Integer = {}
        Call oSurfBody.GetExistingFacets(BestTolerance,_
                                        adVertexCoords,aiVertexIndices)
 
        ' Start a transaction.
        Dim oTrans As Transaction
        oTrans = m_invApp.TransactionManager.StartTransaction(oPartDoc,"Z Height Colors")
 
        ' Create the graphics data sets collection.
        oDataSets = oPartDoc.GraphicsDataSetsCollection.Add("MyTest")
 
        ' Create the coordinate set and set it using the coordinates from the facets.
        Dim oGraphicsCoordSet As GraphicsCoordinateSet
        oGraphicsCoordSet = oDataSets.CreateCoordinateSet(1)
        Call oGraphicsCoordSet.PutCoordinates(adVertexCoords)
 
        ' Create the index set and set it using the indices from the facets.
        Dim oGraphicsIndexSet As GraphicsIndexSet
        oGraphicsIndexSet = oDataSets.CreateIndexSet(2)
        Call oGraphicsIndexSet.PutIndices(aiVertexIndices)
 
        ' Create the normal set and set it using the normals from the facets.
        Dim oGraphicsNormalSet As GraphicsNormalSet
        oGraphicsNormalSet = oDataSets.CreateNormalSet(3)
        Call oGraphicsNormalSet.PutNormals(adNormalVectors)
 
        ' Determine the min-max range of the body in Z.
        Dim dMinZ As Double
        dMinZ = oSurfBody.RangeBox.MinPoint.Z
        Dim dMaxZ As Double
        dMaxZ = oSurfBody.RangeBox.MaxPoint.Z
        Dim dHeightDifference As Double
        dHeightDifference = dMaxZ - dMinZ
 
        ' Allocate the array that will contain the color information.
        ' This array contains RGB values for each vertex.
        Dim abtColors() As Byte
        ReDim abtColors(iVertexCount * 3 - 1)
 
        ' Load the array with color information for each vertex.
        For i = 0 To iVertexCount - 1
            ' Get the Z height of the current vertex.
            Dim dZValue As Double
            dZValue = adVertexCoords(i * 3 + 2)
 
            ' Set the color information for the current vertex.  It's computed by
            ' determining the percentage of the total Z range of the body this vertex
            ' is within.  A color between red and blue is computed based on this percentage.
            ' Blue is at the minimum Z and Red is at the maximum Z with blending between.
            abtColors(i * 3) = ((dZValue - dMinZ) / dHeightDifference) * 255
            abtColors(i * 3 + 1) = 0
            abtColors(i * 3 + 2) = ((dMaxZ - dZValue) / dHeightDifference) * 255
        Next
 
        ' Create the color set and set it using the array of rgb values just created.
        Dim oGraphicsColorSet As GraphicsColorSet
        oGraphicsColorSet = oDataSets.CreateColorSet(4)
        Call oGraphicsColorSet.PutColors(abtColors)
 
        ' Create the client graphics collection.
        Dim oClientGraphics As ClientGraphics
        oClientGraphics = oPartDoc.ComponentDefinition.ClientGraphicsCollection.Add("MyTest")
 
        ' Create a graphics node.
        Dim oGraphicNode As GraphicsNode
        oGraphicNode = oClientGraphics.AddNode(1)
 
        ' Create the triangle graphics.
        Dim oTriangles As TriangleGraphics
        oTriangles = oGraphicNode.AddTriangleGraphics
 
        ' Set varIoUs prroperties of the triangle graphics.
        oTriangles.CoordinateSet = oGraphicsCoordSet
        oTriangles.CoordinateIndexSet = oGraphicsIndexSet
        oTriangles.NormalSet = oGraphicsNormalSet
        oTriangles.NormalBinding = NormalBindingEnum.kPerVertexNormals
        oTriangles.NormalIndexSet = oGraphicsIndexSet
        oTriangles.ColorSet = oGraphicsColorSet
        oTriangles.ColorBinding = ColorBindingEnum.kPerVertexColors
        oTriangles.ColorIndexSet = oGraphicsIndexSet
 
        ' Turn off the display of the body.
        oSurfBody.Visible = False
 
        ' End the transaction.
        oTrans.End()
 
        ' Update the view.
        m_invApp.ActiveView.Update()
    End Sub

VB.NET 中正确使用GetExistin​gFacets

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