AutoCAD .NET中完整刀具轮廓旋转为3D实体的实现难题

我开发了一个AutoCAD自定义命令，可导入刀具的2D轮廓并将其旋转生成3D实体。导入半幅刀具轮廓时，因轮廓处于旋转平面一侧，旋转操作可正常执行；但导入完整刀具轮廓时，由于轮廓中心位于旋转平面上，旋转无法正常完成。

我希望仅维护一份完整轮廓文件，无需额外保存半幅轮廓文件，请问是否可以计算出轮廓的一半区域用于旋转，或是有其他可行的解决方案？

轮廓示例 #

• 完整刀具轮廓：
  
• 半幅刀具轮廓：
  

当前实现代码 #

<CommandMethod("RevolveObject")>
Public Shared Sub RevolveObject()

    Dim doc As Document = AutoCADApp.DocumentManager.MdiActiveDocument
    Dim db As Database = doc.Database
    Dim ed As Editor = doc.Editor

    Using tr As Transaction = db.TransactionManager.StartTransaction()

        Dim pStrOpts As PromptStringOptions = New PromptStringOptions("FilePath: ")
        pStrOpts.AllowSpaces = True
        Dim FileName As PromptResult = ed.GetString(pStrOpts)

        Dim promptPointResult = ed.GetPoint(vbLf & "Specify point: ")
        If promptPointResult.Status <> PromptStatus.OK Then Return
        Dim Origin = promptPointResult.Value

        Dim ObjId As ObjectId
        Dim bt As BlockTable = db.BlockTableId.GetObject(OpenMode.ForRead)
        Dim btr As BlockTableRecord = bt(BlockTableRecord.ModelSpace).GetObject(OpenMode.ForWrite)

        'Import the object
        Using dbInsert As New Database(False, True)
            dbInsert.ReadDwgFile(FileName.StringResult, IO.FileShare.Read, True, "")
            ObjId = db.Insert(Path.GetFileNameWithoutExtension(FileName.StringResult), dbInsert, True)
        End Using

        'Explode the object
        Dim acPoly As BlockReference = New BlockReference(New Point3d(Origin.X, Origin.Y, Origin.Z), ObjId)
        Dim acDBObjColl As DBObjectCollection = New DBObjectCollection()
        acPoly.Explode(acDBObjColl)

        'Revolve the object
        Dim pline As New Solid3d()
        Using plineCollection As New DBObjectCollection()
            plineCollection.Add(pline)
            Using regionCollection As DBObjectCollection = Region.CreateFromCurves(acDBObjColl)
                Using region As Region = DirectCast(regionCollection(0), Region)
                    Using solid As New Solid3d()

                        solid.Layer = 0

                        Dim acVec3d As Vector3d = New Vector3d(0, 0, 10) 'not sure about the 10 but it works
                        solid.Revolve(region, Origin, acVec3d, 360 * (Math.PI / 180))

                        btr.AppendEntity(solid)
                        tr.AddNewlyCreatedDBObject(solid, True)

                    End Using
                End Using
            End Using
        End Using

        tr.Commit()

    End Using

End Sub

方法1：提取半幅轮廓并旋转（推荐） #

利用刀具轮廓的对称性，从完整轮廓中裁剪出半幅区域再执行旋转，步骤如下：

1. 确定轮廓的对称轴（对应旋转轴线，比如X轴）。
2. 创建裁剪边界（沿对称轴的无限长直线）。
3. 拆分轮廓曲线，筛选出对称轴一侧的部分。
4. 用筛选后的曲线生成面域，再旋转成实体。

修改后的核心代码片段：

' 替换原代码中"Revolve the object"部分的内容
' 假设旋转轴线为Origin所在的X轴，裁剪Y≥Origin.Y的区域
Dim clipBoundary As DBObjectCollection = New DBObjectCollection()
Dim xAxisLine As Line = New Line(
    New Point3d(Origin.X - 1000, Origin.Y, Origin.Z),
    New Point3d(Origin.X + 1000, Origin.Y, Origin.Z)
)
clipBoundary.Add(xAxisLine)

Dim clippedCurves As DBObjectCollection = New DBObjectCollection()
For Each curve As Curve In acDBObjColl
    Dim splitCurves As DBObjectCollection = curve.GetSplitCurvesAtIntersection(clipBoundary)
    For Each seg As Curve In splitCurves
        ' 取曲线中点判断所在区域，避免浮点误差
        Dim midPt As Point3d = seg.GetPointAtParameter(seg.EndParameter / 2)
        If midPt.Y >= Origin.Y - 0.001 Then
            clippedCurves.Add(seg)
        End If
    Next
Next

' 生成裁剪后的面域并旋转
If clippedCurves.Count > 0 Then
    Using regionCollection As DBObjectCollection = Region.CreateFromCurves(clippedCurves)
        If regionCollection.Count > 0 Then
            Using region As Region = DirectCast(regionCollection(0), Region)
                Using solid As New Solid3d()
                    solid.Layer = 0
                    ' 使用单位Z向量更规范，直接用2π表示360度
                    Dim acVec3d As Vector3d = Vector3d.ZAxis
                    solid.Revolve(region, Origin, acVec3d, 2 * Math.PI)
                    btr.AppendEntity(solid)
                    tr.AddNewlyCreatedDBObject(solid, True)
                End Using
            End Using
        End If
    End Using
End If

方法2：修复完整轮廓旋转逻辑 #

完整轮廓旋转失败通常是因为轮廓自交、旋转轴线穿过轮廓内部导致实体无效，可以尝试：

• 检查轮廓完整性：确保导入的完整轮廓是单一闭合多段线，无重叠、缺口。
• 调整旋转原点：将旋转原点移至轮廓的对称轴边缘（而非中心），让轮廓整体处于旋转平面一侧。
• 替换旋转方式：先将面域拉伸成薄体，再绕轴线旋转360度，但效率低于裁剪半幅轮廓。

方法3：利用对称镜像 #

如果轮廓严格对称，也可以导入完整轮廓后，沿对称轴删除其中一半，再执行旋转，但本质和方法1一致，步骤更繁琐。

内容的提问来源于stack exchange，提问作者Patrick