问题：我把3d图形转成xaml，拷贝进来之后，发现会报错误，但是点击运行，可以运行，我测试过，如果把
<DiffuseMaterial >
<DiffuseMaterial.Brush >
<SolidColorBrush Color="#B2B200" Opacity="1.000000"/>
</DiffuseMaterial.Brush>
</DiffuseMaterial>
删除掉，就不会报错。不知道是什么原因。
报错内容如下
**引发异常 **
NullReferenceException: 未将对象引用设置到对象的实例。
InnerException: 无
StackTrace
在 Microsoft.Expression.DesignSurface.View.XamlHitTestHelper.WalkHitTestPath(Viewport3D rootViewport, ViewNode currentViewNode, List1 path)1& invisibleHits)
在 Microsoft.Expression.DesignSurface.View.XamlHitTestHelper.Record3DHitTestResult(Viewport3D rootViewport, RectangleHitTestResult summary)
在 Microsoft.Expression.DesignSurface.View.XamlHitTestHelper.FilterPotentialHit(IViewObject viewObject, IParentChainProvider parentChain)
在 Microsoft.Expression.WpfPlatform.ViewObjects.WpfViewVisual.HitTestFilterCallback(DependencyObject potentialHitTestTarget)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTestPoint(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, PointHitTestParameters pointParams)
在 System.Windows.Media.Visual.HitTest(HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, HitTestParameters hitTestParameters)
在 System.Windows.Media.VisualTreeHelper.HitTest(Visual reference, HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, HitTestParameters hitTestParameters)
在 Microsoft.Expression.WpfPlatform.ViewObjects.WpfViewVisual.HitTest(ViewHitTestFilterCallback filterCallback, ViewHitTestResultCallback resultCallback, HitTestParameters hitTestParameters, List
在 Microsoft.Expression.DesignSurface.View.XamlHitTestHelper.PerformHitTest(HitTestParameters hitTestParameters, HitTestModifier hitTestModifier, InvisibleObjectHitTestModifier invisibleObjectHitTestModifier, ICollection1 ignoredElements, Boolean stopAfterFirstHit, Boolean skipFullyContainedSelectionInObject, ViewHitTestFilterCallback filterCallback)1 ignoredElements)
在 Microsoft.Expression.DesignSurface.View.XamlSceneView.GetElementAtPoint(Point point, HitTestModifier hitTestModifier, InvisibleObjectHitTestModifier invisibleObjectHitTestModifier, ICollection
在 Microsoft.Expression.DesignSurface.View.XamlSceneView.HitElementHelper.GetSelectableElementAtPoint(Point point)
在 Microsoft.Expression.DesignSurface.View.XamlSceneView.GetSelectableElementAtPoint(Point point, SelectionFor3D selectionFor3D, Boolean selectedOnly, Boolean smartInvisiblePanelSelect)
在 Microsoft.Expression.DesignSurface.View.SceneView.GetCachedSelectableElementAtPoint(Point point, SelectionFor3D selectionFor3D)
在 Microsoft.Expression.DesignSurface.Tools.ToolBehavior.CachedHitTest(Point pointerPosition)
在 Microsoft.Expression.DesignSurface.Tools.Selection.ElementEditorBehavior.OnHoverOverNonAdorner(Point pointerPosition)
在 Microsoft.Expression.DesignSurface.Tools.ElementToolBehavior.OnHover(Point pointerPosition)
在 Microsoft.Expression.DesignSurface.Tools.EventRouter.ScopeElement_MouseMove(Object sender, MouseEventArgs args)
在 System.Windows.Input.MouseEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
在 System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
在 System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
在 System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
在 System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
在 System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
在 System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
在 System.Windows.Input.InputManager.ProcessStagingArea()
在 System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
在 System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
在 System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
在 System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
在 System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
在 MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
在 MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
在 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
在 MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
下面这个是源代码：
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="596.269" Width="1025">
<Grid>
<Viewport3D >
<Viewport3D.Camera>
<OrthographicCamera Position="0.005436,0.006462,0.004638" LookDirection="-0.577382,-0.577288,-0.577382" UpDirection="-0.408204,0.816541,-0.408204" NearPlaneDistance="0.003497" FarPlaneDistance="0.010491" Width="0.026994"/>
</Viewport3D.Camera>
<Viewport3D.Children>
<ModelVisual3D >
<ModelVisual3D.Transform>
<RotateTransform3D>
<RotateTransform3D.Rotation>
<AxisAngleRotation3D Angle="0" Axis="0,1,0"/>
</RotateTransform3D.Rotation>
</RotateTransform3D>
</ModelVisual3D.Transform>
<ModelVisual3D.Children>
<ModelVisual3D>
<ModelVisual3D.Content>
<Model3DGroup x:Name="test">
<Model3DGroup.Children>
<AmbientLight Color="#262626"/>
<DirectionalLight Color="#6F6F6F" Direction="3.150000,-8.090000,-4.960000"/>
<DirectionalLight Color="#454545" Direction="8.610000,4.820000,-1.640000"/>
<DirectionalLight Color="#332835" Direction="-9.490000,3.090000,0.600000"/>
</Model3DGroup.Children>
</Model3DGroup>
</ModelVisual3D.Content>
</ModelVisual3D>
<ModelVisual3D>
<ModelVisual3D.Transform>
<MatrixTransform3D Matrix="1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 "/>
</ModelVisual3D.Transform>
<ModelVisual3D.Content>
<Model3DGroup>
<Model3DGroup.Children>
<GeometryModel3D>
<GeometryModel3D.Material >
<MaterialGroup>
<DiffuseMaterial >
<DiffuseMaterial.Brush >
<SolidColorBrush Color="#B2B200" Opacity="1.000000"/>
</DiffuseMaterial.Brush>
</DiffuseMaterial>
<SpecularMaterial SpecularPower="0.200000">
<SpecularMaterial.Brush >
<SolidColorBrush Color="#333300" Opacity="1.000000"/>
</SpecularMaterial.Brush>
</SpecularMaterial>
</MaterialGroup>
</GeometryModel3D.Material>
<GeometryModel3D.Geometry>
<MeshGeometry3D Positions="0.000817,-0.000042,0.000578 0.000817,-0.000044,0.000577 0.000188,-0.000044,0.000577 0.000814,-0.000025,0.000599 0.000813,-0.000025,0.000598 0.000188,-0.000027,0.000594 0.000814,-0.000027,0.000595 0.000814,-0.000025,0.000599 0.000188,-0.000027,0.000594 0.000814,-0.000026,0.000600 0.000188,-0.000026,0.000600 0.000814,-0.000026,0.000601 0.000188,-0.000027,0.000606 0.000814,-0.000027,0.000606 0.000815,-0.000029,0.000612 0.000814,-0.000027,0.000606 0.000188,-0.000029,0.000612 0.000188,-0.000029,0.000612 0.000814,-0.000027,0.000606 0.000188,-0.000027,0.000606 0.000814,-0.000027,0.000606 0.000814,-0.000027,0.000606 0.000815,-0.000033,0.000616 0.000815,-0.000029,0.000612 0.000188,-0.000029,0.000612 0.000815,-0.000029,0.000612 0.000815,-0.000029,0.000612 0.000815,-0.000033,0.000616 0.000188,-0.000029,0.000612 0.000815,-0.000033,0.000617 0.000188,-0.000033,0.000617 0.000816,-0.000037,0.000620 0.000816,-0.000037,0.000620 0.000188,-0.000033,0.000617 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</GeometryModel3D.Geometry>
</GeometryModel3D>
</Model3DGroup.Children>
</Model3DGroup>
</ModelVisual3D.Content>
<ModelVisual3D.Children/>
</ModelVisual3D>
</ModelVisual3D.Children>
</ModelVisual3D>
</Viewport3D.Children>
</Viewport3D>
</Grid>
