Thanks to Kurt Berglund for helping to provide this sample.
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<StackPanel>
<Label>X</Label>
<Slider Name="sliderX" Minimum="0" Maximum="5" Value="1"/>
<Label>Y</Label>
<Slider Name="sliderY" Minimum="0" Maximum="5" Value="1"/>
<Label>Z</Label>
<Slider Name="sliderZ" Minimum="0" Maximum="5" Value="1"/>
<Viewport3D Width="200" Height="200">
<Viewport3D.Camera>
<PerspectiveCamera LookDirection = "-4, -4, -4"
UpDirection = "0, 1, 0"
Position = "4, 4, 4"
FieldOfView = "45" />
</Viewport3D.Camera>
<ModelVisual3D>
<ModelVisual3D.Children>
<ModelVisual3D>
<ModelVisual3D.Content>
<DirectionalLight Color="#FFFFFF" Direction="-0.5,-0.3,-1"/>
</ModelVisual3D.Content>
</ModelVisual3D>
<ModelVisual3D>
<ModelVisual3D.Transform>
<Transform3DGroup>
<Transform3DGroup.Children>
<ScaleTransform3D CenterX="0" CenterY="0" CenterZ="0"
ScaleX="{Binding ElementName=sliderX,Path=Value}" ScaleY="1" ScaleZ="1" />
<ScaleTransform3D CenterX="0" CenterY="0" CenterZ="0"
ScaleY="{Binding ElementName=sliderY,Path=Value}" ScaleX="1" ScaleZ="1" />
<ScaleTransform3D CenterX="0" CenterY="0" CenterZ="0"
ScaleZ="{Binding ElementName=sliderZ,Path=Value}" ScaleX="1" ScaleY="1" />
</Transform3DGroup.Children>
</Transform3DGroup>
</ModelVisual3D.Transform>
<ModelVisual3D.Content>
<GeometryModel3D>
<GeometryModel3D.Geometry>
<MeshGeometry3D TriangleIndices = "0,1,2 2,3,0
4,7,6 6,5,4
8,11,10 10,9,8
12,13,14 14,15,12
16,17,18 18,19,16
20,23,22 22,21,20"
Positions = "-1,-1,1 -1,-1,-1 1,-1,-1 1,-1,1
-1,1,1 -1,1,-1 1,1,-1 1,1,1
-1,-1,1 -1,1,1 1,1,1 1,-1,1
-1,-1,-1 -1,1,-1 1,1,-1 1,-1,-1
-1,-1,1 -1,1,1 -1,1,-1 -1,-1,-1
1,-1,1 1,1,1 1,1,-1 1,-1,-1" />
</GeometryModel3D.Geometry>
<GeometryModel3D.Material>
<DiffuseMaterial>
<DiffuseMaterial.Brush>
<SolidColorBrush Color="Green" />
</DiffuseMaterial.Brush>
</DiffuseMaterial>
</GeometryModel3D.Material>
</GeometryModel3D>
</