WPF ViewPort3D ModelVisual3D GeometryModel3D MeshGeometry3D Positions Normals

<Window x:Class="WpfApp107.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp107"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Viewport3D>
        <Viewport3D.Camera>
            <PerspectiveCamera Position="0,0,5"
                               LookDirection="0,0,-1"
                               UpDirection="0,1,0"/>
        </Viewport3D.Camera>
        <ModelVisual3D>
            <ModelVisual3D.Content>
                <!--<GeometryModel3D>
                    <GeometryModel3D.Geometry>
                        <MeshGeometry3D Positions="0,0,0 1,0,0 0,1,0 0,0,1"
                                        TriangleIndices="0,1,2 0,2,3 0,3,1 1,3,2"/>
                    </GeometryModel3D.Geometry>
                    <GeometryModel3D.Material>
                        <DiffuseMaterial Brush="Blue"/>
                    </GeometryModel3D.Material>
                </GeometryModel3D>-->
                <GeometryModel3D>
                    <GeometryModel3D.Geometry>
                        <MeshGeometry3D 
              Positions="-1 -1 0  1 -1 0  -1 1 0  1 1 0"
              Normals="0 0 1  0 0 1  0 0 1  0 0 1"
              TextureCoordinates="0 1  1 1  0 0  1 0   "
              TriangleIndices="0 1 2  1 3 2" />
                    </GeometryModel3D.Geometry>
                    <GeometryModel3D.Material>
                        <DiffuseMaterial>
                            <DiffuseMaterial.Brush>
                                <SolidColorBrush Color="Cyan" Opacity="0.3"/>
                            </DiffuseMaterial.Brush>
                        </DiffuseMaterial>
                    </GeometryModel3D.Material>
                    <!-- Translate the plane. -->
                    <GeometryModel3D.Transform>
                        <TranslateTransform3D
            OffsetX="2" OffsetY="0" OffsetZ="-1"   >
                        </TranslateTransform3D>
                    </GeometryModel3D.Transform>
                </GeometryModel3D>
            </ModelVisual3D.Content>
        </ModelVisual3D>
        <ModelVisual3D>
            <ModelVisual3D.Content>
                <AmbientLight Color="White"/>
            </ModelVisual3D.Content>
        </ModelVisual3D>
    </Viewport3D>
</Window>