Smoothing of Vertices in MeshGeometry3D (WPF)

Question

Hi

I'm porting a DirectX application into WPF, using the Windows.Media.Media3D toolkit. Which is working good and all, except that the Model is rendered in-complete, even when it have gotten all possible data.

I suspect it's because DirectX optimize and somehow smooth or help rendering additional content depending on the vertices and indicies.

So I'm wondering if there's a option to change how WPF renders 3D models? It's a bit hard to express precisely what I mean, but I hope it's somehow understandable.

Here's the important code:

private void DrawModel()
{
    SwordModel swordModel;

    string filename = "PG_S8_02";

    using(FileStream stream = File.OpenRead(string.Format("Media/Models/{0}.gb", filename)))
    using(BinaryReader reader = new BinaryReader(stream))
    {
        swordModel = new SwordModel(reader);         
    }

    var group = new Model3DGroup();

    foreach(var modelMesh in swordModel.Meshes)
    {
        var mesh3D = new MeshGeometry3D();

        // Indices
        foreach(var index in modelMesh.Indices)
        {
            mesh3D.TriangleIndices.Add(index);
        }

        // Vertices
        foreach(var vertex in modelMesh.Vertices)
        {
            mesh3D.Positions.Add(vertex);
        }

        // Normals
        foreach(var normal in modelMesh.Normals)
        {
            mesh3D.Normals.Add(normal);
        }

        // Texture Coordinates
        foreach(var vertex in modelMesh.Vertices)
        {
            mesh3D.TextureCoordinates.Add(new Point(vertex.X, vertex.Y));
        }

        // Material
        var material = new DiffuseMaterial();
        var texture  = new BitmapImage(new Uri(
            string.Format("Media/Textures/{0}.png", filename), 
            UriKind.RelativeOrAbsolute
        ));   
        material.Brush = new ImageBrush(texture);                               

        // Add to View
        group.Children.Add(
            new GeometryModel3D(mesh3D, material)
        );
    }    

    mainViewport.Children.Add(
        new ModelVisual3D() { Content = group }
    );         
}

And XAML:

<Viewport3D Name="mainViewport" ClipToBounds="True">
    <Viewport3D.Camera>
        <PerspectiveCamera 
            FarPlaneDistance="100"
                        LookDirection="-11,-10,-9"
                        UpDirection="0,1,0"
                        NearPlaneDistance="1" 
                        Position="11,10,9" 
                        FieldOfView="70" />
    </Viewport3D.Camera>
    <ModelVisual3D>
        <ModelVisual3D.Content>
            <DirectionalLight Color="White" Direction="-2,-3,-1" />
        </ModelVisual3D.Content>
    </ModelVisual3D>
</Viewport3D>

Answer 1

Is there a problem with sidedness? By default I think WPF renders facets onesided - you can't see them from the 'wrong' side.

Similarly with lighting you can get odd effects if your model isn't illuminated from all directions - try putting in an AmbientLight

Answer 2

The only thing I can think of is that the normals aren't smoothed, but without seeing what the mesh looks like I couldn't say for sure.

By that I mean that the vertex normals are parallel to the face normals giving the mesh a faceted look. If the normals are smoothed then the whole shape looks smoothed. Something like this:

Flat Shading:

http://www.forman.free-online.co.uk/images/flatshading.png

Smooth Shading:

http://www.forman.free-online.co.uk/images/smoothshading.png

images replaced by links to limit my bandwidth usage