A Xaml spinner template with a polar gradient

spinner.xaml

 <ControlTemplate x:Key="BusyIndicatorProgressBarControlTemplate" TargetType="telerik:RadProgressBar">
        <Grid>
            <VisualStateManager.VisualStateGroups>
                <VisualStateGroup x:Name="CommonStates">
                    <VisualState x:Name="Determinate"/>
                    <VisualState x:Name="Indeterminate">
                        <Storyboard RepeatBehavior="Forever">
                            <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Storyboard.TargetName="IndeterminateDonut" Storyboard.TargetProperty="(UIElement.RenderTransform).(TransformGroup.Children)[0].(RotateTransform.Angle)">
                                <SplineDoubleKeyFrame KeyTime="00:00:01" Value="360"/>
                            </DoubleAnimationUsingKeyFrames>
                        </Storyboard>
                    </VisualState>
                </VisualStateGroup>
            </VisualStateManager.VisualStateGroups>
            <Grid.Resources>
                <x:Array x:Key="sampleData" Type="sys:Object">
                    <x:Array Type="sys:Object">
                        <sys:Double>0</sys:Double>
                        <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                            <GradientStop Color="#000C528C" Offset="0"/>
                            <GradientStop Color="#440C528C" Offset="1"/>
                        </LinearGradientBrush>
                    </x:Array>
                    <x:Array Type="sys:Object">
                        <sys:Double>90</sys:Double>
                        <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                            <GradientStop Color="#440C528C" Offset="0"/>
                            <GradientStop Color="#880C528C" Offset="1"/>
                        </LinearGradientBrush>
                    </x:Array>
                    <x:Array Type="sys:Object">
                        <sys:Double>180</sys:Double>
                        <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                            <GradientStop Color="#880C528C" Offset="0"/>
                            <GradientStop Color="#BB0C528C" Offset="1"/>
                        </LinearGradientBrush>
                    </x:Array>
                    <x:Array Type="sys:Object">
                        <sys:Double>270</sys:Double>
                        <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                            <GradientStop Color="#BB0C528C" Offset="0"/>
                            <GradientStop Color="#FF0C528C" Offset="1"/>
                        </LinearGradientBrush>
                    </x:Array>
                </x:Array>
            </Grid.Resources>
            <ItemsControl ItemsSource="{StaticResource sampleData}" Height="22" Width="22" RenderTransformOrigin="0.5,0.5" x:Name="IndeterminateDonut">
                <ItemsControl.RenderTransform>
                    <TransformGroup>
                        <RotateTransform/>
                    </TransformGroup>
                </ItemsControl.RenderTransform>
                <ItemsControl.OpacityMask>
                    <RadialGradientBrush>
                        <GradientStop Color="Transparent" Offset="0.95"/>
                        <GradientStop Color="White" Offset="0.949"/>
                        <GradientStop Color="White" Offset="0.601"/>
                        <GradientStop Color="Transparent" Offset="0.6"/>
                    </RadialGradientBrush>
                </ItemsControl.OpacityMask>
                <ItemsControl.Template>
                    <ControlTemplate TargetType="ItemsControl">
                        <ItemsPresenter/>
                    </ControlTemplate>
                </ItemsControl.Template>
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <Canvas/>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <Canvas Width="1" Height="1">
                            <Canvas.RenderTransform>
                                <RotateTransform Angle="{Binding [0]}" CenterX="11" CenterY="11"/>
                            </Canvas.RenderTransform>
                            <Viewport3D Width="22.07" Height="22.07">
                                <ModelVisual3D>
                                    <ModelVisual3D.Content>
                                        <Model3DGroup>
                                            <GeometryModel3D>
                                                <GeometryModel3D.Geometry>
                                                    <MeshGeometry3D Positions="0 0 0, 0 1 0, 1 0 0, 1 1 0" TextureCoordinates="0 1, 0 0, 1 1, 1 0" TriangleIndices="0 2 1, 2 3 1"/>
                                                </GeometryModel3D.Geometry>
                                                <GeometryModel3D.Material>
                                                    <DiffuseMaterial Brush="{Binding [1]}"/>
                                                </GeometryModel3D.Material>
                                                <GeometryModel3D.Transform>
                                                    <MatrixTransform3D Matrix="0.002,0,0,0,-0.499,-0.498,0,-0.998,0,0,1,0,0.499,0.5,0,1"/>
                                                </GeometryModel3D.Transform>
                                            </GeometryModel3D>
                                            <AmbientLight Color="White" />
                                        </Model3DGroup>
                                    </ModelVisual3D.Content>
                                </ModelVisual3D>
                                <Viewport3D.Camera>
                                    <OrthographicCamera Position="0.5 0.5 1" LookDirection="0 0 -1" UpDirection="0 1 0" Width="1"/>
                                </Viewport3D.Camera>
                            </Viewport3D>
                        </Canvas>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </Grid>
    </ControlTemplate>