Setting Opacity for ObjectModel3D

I have a 3D chart where we are loading .obj files. If I set the opacity on the element in Xaml it works. However, we want to be able to adjust the opacity with a slider. When we bind the opacity to the value of the slider the opacity does not change. Is there something else we need to do to get the opacity to change when the slider value changes? The slider has a minimum of 0 and a maximum of 1.

<s3D:SciChart3DSurface x:Name="ThreeDChart"
                           IsAxisCubeVisible="False"
                           IsFpsCounterVisible="False"
                           IsXyzGizmoVisible="True"
                           ShowLicensingWarnings="False">
<s3D:SciChart3DSurface.XAxis>
    <s3D:NumericAxis3D />
</s3D:SciChart3DSurface.XAxis>
<s3D:SciChart3DSurface.YAxis>
    <s3D:NumericAxis3D />
</s3D:SciChart3DSurface.YAxis>
<s3D:SciChart3DSurface.ZAxis>
    <s3D:NumericAxis3D />
</s3D:SciChart3DSurface.ZAxis>
<s3D:SciChart3DSurface.SceneObjects>
    <object:ObjectModel3D x:Name="BrainMesh"
                          CoordinateMode="Relative"
                          Opacity="{Binding BrainOpacity}"
                          Position="0.5, 0.5, 0.5"
                          Scale="5, 5, 5"
                          Source="{StaticResource Brain}" />
</s3D:SciChart3DSurface.SceneObjects>
<s3D:SciChart3DSurface.ChartModifier>
    <s3D:ModifierGroup3D>
        <s3D:OrbitModifier3D />
        <s3D:ZoomExtentsModifier3D />
    </s3D:ModifierGroup3D>
</s3D:SciChart3DSurface.ChartModifier>

Thank you!