Opening volume views in certain ways makes it so that the 3D content is not visible on the LKG.

From Albert:

> Open Slicer
> Use MRHead from the Sample Data module
> Go to the "Data" module
> Right click on the "Show/hide branch or node" item for MRHead
> Select "Show in 3D views as volume rendering"
> The scan of the head will show in the 2D display, but will not show in the LKG.

Reproduce the issue in Slicer with MRHead from Sample Data, then use the Data module's “Show in 3D views as volume rendering” action. Trace the volume-rendering path that updates the 2D display and the Looking Glass (LKG) view; done means the head scan appears in the LKG as well as the 2D display.

Written by the indexing model from the issue text.