Hi Jack!
So I've just spent some time replicating what you've got going on on your end, and what is happening is less related to the 3D Transformations themselves, but related to the fact that clipping takes place at the 2D level before its rendered in 3D. So, basically, if an Element is clipped in 2D by its container, it will also be in 3D. And that is what's occurring here.
Essentially, the height of your ItemsControl is not tall enough to accommodate all of the items within, which is where the clipping in this situation is happening.
The simplest way to solve this is to simply wrap your ItemsControl into a Canvas Element. Since Canvas Elements never clip their children, your ItemsControl will then find spatial freedom.
Now one thing that will happen when you wrap the ItemsControl into this Canvas, is that your alignment will get all out-of-whack from its original central positioning.
To resolve this, you will want to do the following:
1) Set your Canvas to have a Horizontal Alignment of "Center".
2) In the Canvas' Width Property, bind its Width Property to the 'ActualWidth' of your ItemsControl. (You will have to name your ItemsControl before doing this, so that it can be targeted by name)
This is what all this looks like after I had initially started with a visual result similar to yours (with the top of the ItemsControl clipped):
Let me know if this this resolves things for you, or if we need to look further.
- Dorian
