SOLIDWORKS macro to find the geometrical difference between parts

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This macro allows to compare two parts by its geometry.

IBody2::GetCoincidenceTransform2 SOLIDWORKS API is used to compare bodies and if equal find the transformation between them.


  • Macro supports multi-bodies parts
  • Macro will compare the bodies even if they are located in different position (i.e. moved or rotated) in the comparable parts.
  • Comparable parts might have different number of bodies
  • Macro will try to find the most suitable transformation between two parts


Original part to be compared:

Original part
Original part

Part to compare

Part to compare
Part to compare

Second part has a modified geometry and was reoriented in space. Some of the bodies have been deleted from the second part.

The following result is calculated by the macro:

Resulting Difference file
Resulting Difference file


  • Open the original part file
  • Run the macro.
  • Specify the full path for the part file to compare to
  • As the result second part is displayed within the original part
  • Continue the macro (F5) to clear the preview

Dim swApp As SldWorks.SldWorks

Sub main()

    Set swApp = Application.SldWorks
    Dim swPart As SldWorks.PartDoc
    Set swPart = swApp.ActiveDoc
    If Not swPart Is Nothing Then
        Dim otherFilePath As String
        otherFilePath = InputBox("Please specify the part path to compare to")
        If otherFilePath <> "" Then
            Dim swOtherPart As SldWorks.PartDoc
            Set swOtherPart = swApp.OpenDoc6(otherFilePath, swDocumentTypes_e.swDocPART, swOpenDocOptions_e.swOpenDocOptions_Silent, "", 0, 0)
            If Not swOtherPart Is Nothing Then
                Dim swXform As SldWorks.MathTransform
                Set swXform = GetClosestTransform(swPart, swOtherPart)
                PreviewPart swOtherPart, swXform, swPart
                MsgBox "Failed to open the part to compare to"
            End If
        End If
        MsgBox "Please open part"
    End If
End Sub

Sub PreviewPart(part As SldWorks.PartDoc, transform As SldWorks.MathTransform, context As PartDoc)
    Dim vBodies As Variant
    vBodies = part.GetBodies2(swBodyType_e.swSolidBody, True)
    Dim i As Integer
    For i = 0 To UBound(vBodies)
        Dim swBody As SldWorks.Body2
        Set swBody = vBodies(i)
        Set swBody = swBody.Copy
        If Not transform Is Nothing Then
            Debug.Print swBody.ApplyTransform(transform)
        End If
        Set vBodies(i) = swBody
        swBody.Display3 context, RGB(255, 255, 0), swTempBodySelectOptions_e.swTempBodySelectOptionNone
    Stop 'continue the macro to hide preview
End Sub

Function GetClosestTransform(thisPart As SldWorks.PartDoc, otherPart As SldWorks.PartDoc) As SldWorks.MathTransform

    Dim vThisBodies As Variant
    Dim vOtherBodies As Variant
    vThisBodies = thisPart.GetBodies2(swBodyType_e.swSolidBody, True)
    vOtherBodies = otherPart.GetBodies2(swBodyType_e.swSolidBody, True)
    Dim transformsHits As Object
    Set transformsHits = CreateObject("Scripting.Dictionary") 'by some reasons sometimes the first null element is added on creation
    If Not IsEmpty(vThisBodies) And Not IsEmpty(vOtherBodies) Then
        Dim i As Integer
        Dim j As Integer
        For i = 0 To UBound(vOtherBodies)
            Dim swOtherBody As SldWorks.Body2
            Set swOtherBody = vOtherBodies(i)
            For j = 0 To UBound(vThisBodies)
                Dim swThisBody As SldWorks.Body2
                Set swThisBody = vThisBodies(j)
                Dim swTransform As SldWorks.MathTransform
                If swThisBody.GetCoincidenceTransform2(swOtherBody, swTransform) Then
                    If Not swTransform Is Nothing Then
                        Dim contains As Boolean
                        contains = False
                        For Each key In transformsHits.Keys
                            If Not key Is Nothing Then
                                Dim tx As SldWorks.MathTransform
                                Set tx = key
                                If CompareTransforms(swTransform, tx) Then
                                    transformsHits(tx) = transformsHits(tx) + 1
                                    contains = True
                                    Exit For
                                End If
                            End If
                        If Not contains Then
                            transformsHits.Add swTransform, 1
                        End If
                    End If
                End If
    End If
    Dim curMaxHit As Integer
    curMaxHit = 0
    For Each key In transformsHits.Keys
        If Not key Is Nothing Then
            Dim curTx As SldWorks.MathTransform
            Set curTx = key
            If transformsHits(curTx) > curMaxHit Then
                curMaxHit = transformsHits(curTx)
                Set GetClosestTransform = curTx
            End If
        End If

End Function

Function CompareTransforms(firstTransform As SldWorks.MathTransform, secondTransform As SldWorks.MathTransform) As Boolean
    Dim vFirstArrayData As Variant
    vFirstArrayData = firstTransform.ArrayData
    Dim vSecondArrayData As Variant
    vSecondArrayData = secondTransform.ArrayData
    Dim i As Integer
    For i = 0 To UBound(vFirstArrayData)
        If Not CompareValues(CDbl(vFirstArrayData(i)), CDbl(vSecondArrayData(i))) Then
            CompareTransforms = False
            Exit Function
        End If
    CompareTransforms = True
End Function

Function CompareValues(firstValue As Double, secondValue As Double, Optional tol As Double = 0.00000001) As Boolean
    CompareValues = Abs(secondValue - firstValue) <= tol
End Function

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