I have discovered an effective way to make sure you follow up on your promises: arrange to have them captured on video.  I had not been able to find the 15 minutes to try Rob’s suggestion for inserting a resource into a collection since November, but somehow tonight was different.  I actually heard from the community before I received the internal email notifying me that the segment had been posted.  :)

Here is the updated source which no longer uses the WindowsLoaded event.  It’s now 100% Xaml.  The trick I was missing was the <x:Include x:Content="{ball}" /> which is a Xaml element that evaluates to a reference to the resource named “ball”.  This allows me to take the same animated bouncing ball model and insert it into two Viewport3Ds to efficiently create the mirroring effect in Xaml which I was previously falling back to C# in the code-behind to do.