title: Constraining dimension of a PlaneProjection
body: <p>How can I constrain a plane projection to a particular dimension? For example, I have the following:</p>
  
  <pre><code>    &lt;Canvas  Width="720" Height="540" x:Name="Root" Background="Red"  &gt;
          &lt;Line Width="200" Height="5" X1="0" X2="200" 
              Y1="0" Y2="0" Stroke="LimeGreen" StrokeThickness="10"
              Canvas.Left="260" Canvas.Top="70" /&gt;
          &lt;Rectangle Width="200" Height="400" Stroke="Blue" StrokeThickness="6" 
              Fill="LightBlue"  Opacity="0.5" Canvas.Left="260" Canvas.Top="70"&gt;
              &lt;Rectangle.Projection&gt;
                  &lt;PlaneProjection x:Name="box" /&gt;
              &lt;/Rectangle.Projection&gt;
          &lt;/Rectangle&gt;
          &lt;Line Width="200" Height="10" X1="0" X2="200" 
              Y1="0" Y2="0" Stroke="LimeGreen" StrokeThickness="10"
              Canvas.Left="260" Canvas.Top="464" /&gt;
      &lt;/Canvas&gt;
  </code></pre>
  
  <p>I want to rotate this around its Y axis by 360 degrees, but never want the projection to exceed the bounds of the height of the rectangle - in this case, 400 points.</p>
  
  <p>The storyboard, just for simplicities' sake in testing, is in a trigger.</p>
  
  <pre><code>&lt;UserControl.Triggers&gt;
      &lt;EventTrigger&gt;
          &lt;BeginStoryboard&gt;
              &lt;Storyboard&gt;
                  &lt;DoubleAnimation Storyboard.TargetName="box"
                                   Storyboard.TargetProperty="RotationY"
                                   By="360" Duration="0:0:15"
                                   RepeatBehavior="Forever" /&gt;
              &lt;/Storyboard&gt;
          &lt;/BeginStoryboard&gt;
      &lt;/EventTrigger&gt;
  &lt;/UserControl.Triggers&gt;
  </code></pre>