public struct VertexPositionNormalColored
    {
        public Vector3 Position;
        public Color Color;
        public Vector3 Normal;

        public static int SizeInBytes = 7 * 4;
        public static VertexElement[] VertexElements = new VertexElement[]
          {
          new VertexElement( 0, 0, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Position, 0 ),
          new VertexElement( 0, sizeof(float) * 3, VertexElementFormat.Color, VertexElementMethod.Default, VertexElementUsage.Color, 0 ),
          new VertexElement( 0, sizeof(float) * 4, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Normal, 0 ),
          };
    }