Question

With WPF 3D, is it possible to have a texture with an alpha channel?

I am wanting to make a 3d scene where everything is flat surfaces (like everything is paper cutouts). I thought the easiest way to achieve this would be to create a plane, divide it into quite a few triangle (like a cloth), then apply a texture with a transparent background. This way I could use the same geometry and just swap out the texture to get completely different shapes.

I tried adding a PNG with a transparent background to a model as a brush, but it shows up with a white background. Does WPF 3D provide this functionality? how can it be done?

Answer 1

texture with alpha does works in wpf ( it works for me ! ).
are you sure your png alpha is ok ?

a png with alpha in a DiffuseMaterial il all you need.
here’s a chunk of xaml with a camera over two textured planar meshes.

replace the path of the png, put it in a xaml file and launch.
you should be able to see material2 behind alpha of material1.

<Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="640.0" Height="480.0"   >
  <Grid.Resources>
    <MeshGeometry3D x:Key="Mesh" Positions="-4.999,-4.999,0.001 5.001,-4.999,0.001 -4.999,5.001,0.001 5.001,5.001,0.001 " TriangleIndices="2 0 3  1 3 0  " TextureCoordinates="0,0 1,0 0,1 1,1 "  />

      <DiffuseMaterial x:Key="material1" >
        <DiffuseMaterial.Brush>
          <ImageBrush ImageSource="C:\mypng.png" Transform="1,0,0,-1,0,1" />
        </DiffuseMaterial.Brush>
      </DiffuseMaterial>

      <DiffuseMaterial x:Key="material2" >
        <DiffuseMaterial.Brush>
         <ImageBrush ImageSource="C:\image_4.png"  Transform="1,0,0,-1,0,1"  />
        </DiffuseMaterial.Brush>
      </DiffuseMaterial>

  </Grid.Resources>
  <Viewport3D Width="640.0" Height="480.0" >
    <Viewport3D.Camera>
      <PerspectiveCamera  Position="0,0,20"/>
    </Viewport3D.Camera>

    <ModelVisual3D>
      <ModelVisual3D.Content>
        <Model3DGroup >

            <AmbientLight />

            <GeometryModel3D Geometry="{StaticResource Mesh}" Material="{StaticResource material2}">
             <GeometryModel3D.Transform>
              <MatrixTransform3D Matrix="1.0,0.0,0.0,0,0.0,1.0,0.0,0,0.0,0.0,1.0,0,0.0,0.0,-5.0,1" />
            </GeometryModel3D.Transform>
            </GeometryModel3D>

            <GeometryModel3D Geometry="{StaticResource Mesh}" Material="{StaticResource material1}">
            <GeometryModel3D.Transform>
              <MatrixTransform3D Matrix="1.0,0.0,0.0,0,0.0,1.0,0.0,0,0.0,0.0,1.0,0,0.0,0.0,0.0,1" />
            </GeometryModel3D.Transform>
            </GeometryModel3D>

        </Model3DGroup>
      </ModelVisual3D.Content>
    </ModelVisual3D>
  </Viewport3D>
</Grid>