Image scaling quality on 3D surface problem in WPF

Question

I have an image viewer created with WPF 3D graphics. Image quality is really WORSE there, so I've started researching this issue, created simple application which shows the image using 2D graphics on the top part of the window, and the same image on the bottom part using 3D graphics. I noticed that image looks much worse on 3D surface than on 2D. The colors on the 3D surface are less saturated and do not have clear boundaries. Note, that I applied linear bitmap scaling mode to the root Grid. Other weird thing is that when I'm changing bitmap scaling mode to 'Fant' or 'NearestNeighbor' it affects 2D graphics, but image on the 3D surface REMAINS THE SAME! I'm using image for this sample with Height = 466px, Width = 490px. I'm zooming out it in the code (both 2D and 3D implementation) a little bit to see the scaling quality degradation. The code is:

<Window x:Class="Scaling3DSample.Window2"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="340">
        <Grid x:Name="backgroundGrid">
            <Grid.RowDefinitions>
                <RowDefinition />
                <RowDefinition />
            </Grid.RowDefinitions>
        </Grid>
</Window>

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Media.Media3D;
using System.Windows.Shapes;
    namespace Scaling3DSample
    {
        public partial class Window2 : Window
        {
            private static double _distanceFromCamera = 0.62618;

            public Window2()
            {
                InitializeComponent();
                RenderOptions.SetBitmapScalingMode(backgroundGrid, BitmapScalingMode.Linear);
                Create2DGraphics();
                // THE SAME IMAGE ON 3D SURFACE LOOKS MUCH WORSE
                Create3DGraphics();
            }

            private void Create2DGraphics()
            {
                Rectangle exampleRectangle = new Rectangle();
                Grid.SetRow(exampleRectangle, 0);

                exampleRectangle.Width = 335;
                exampleRectangle.Height = 317;
                exampleRectangle.Fill = GetBrush();
                backgroundGrid.Children.Add(exampleRectangle);
            }

            private void Create3DGraphics()
            {
                Viewport3D mainViewPort3D = new Viewport3D();
                Grid.SetRow(mainViewPort3D, 1);

                mainViewPort3D.Camera = new PerspectiveCamera { LookDirection = new Vector3D(-1, 0, 0), UpDirection = new Vector3D(0, 0, 1), FieldOfView = 77.0942 };
                mainViewPort3D.Children.Add(new ModelVisual3D { Content = new AmbientLight() });

                MeshGeometry3D geometry3D = new MeshGeometry3D();

                Point3D topLeft = new Point3D(-_distanceFromCamera, 0.5, -0.5);
                Point3D bottomRight = new Point3D(-_distanceFromCamera, -0.5, 0.5);

                geometry3D.Positions.Add(bottomRight);
                geometry3D.Positions.Add(new Point3D(-_distanceFromCamera, topLeft.Y, bottomRight.Z));
                geometry3D.Positions.Add(new Point3D(-_distanceFromCamera, bottomRight.Y, topLeft.Z));
                geometry3D.Positions.Add(topLeft);

                geometry3D.TriangleIndices.Add(1);
                geometry3D.TriangleIndices.Add(0);
                geometry3D.TriangleIndices.Add(2);

                geometry3D.TriangleIndices.Add(2);
                geometry3D.TriangleIndices.Add(3);
                geometry3D.TriangleIndices.Add(1);

                geometry3D.TextureCoordinates.Add(new Point(0, 0));
                geometry3D.TextureCoordinates.Add(new Point(1, 0));
                geometry3D.TextureCoordinates.Add(new Point(0, 1));
                geometry3D.TextureCoordinates.Add(new Point(1, 1));

                Material material = new DiffuseMaterial(GetBrush());

                ModelVisual3D modelForGeometry = new ModelVisual3D { Content = new GeometryModel3D(geometry3D, material) };
                mainViewPort3D.Children.Add(modelForGeometry);
                backgroundGrid.Children.Add(mainViewPort3D);
            }

            private ImageBrush GetBrush()
            {
            // put any other image URI here, image Height = 466px, Width = 490px
                ImageBrush brush = new ImageBrush(new BitmapImage(new Uri("lion.jpg", UriKind.Relative)));
                brush.Stretch = Stretch.Fill;
                return brush;
            }
        }
    }

Thanks in advance for all your help!

Answer 1

There are some other variables to consider, then.

Your graphics card settings could be forcing the interpolation mode down despite WPF's request for something nicer looking. WPF's 3D is hardware accelerated on Tier 2 hardware, so check your drivers' control software. It might not be possible for WPF to request anything better!

Try enabling anti-aliasing in your application and graphics card settings, too.

Answer 2

Just guessing: you did not define any lights nor any normals. Sometimes that will cause a darker image than you would expect.