Arrange code for implementation of ray in portal functionalities.
Add VirtualDisplayGroup and combine multiple portals in the scenegraph.
First implementation of virtual display groups working on client side.
Rework over portal transit after restructuring.
Fix deletion functionality of virtual display groups.
Adjust PortalCamera to work with new portal structure.
Rename Portal to VirtualDisplay.
Minor naming adjustments.
Commenting of the modified virtual display group structure.
Resolve merge conflict.
Adapt configuration files to new virtual display structure.
Create proper virtual tool representations. Visibility still to be done.
Adjust visibilities of tools in virtual displays.
Fix portal visibility table bug.
First bugfixing of intersection in portal.
Fix portal camera client startup bug when no other virtual display is present.
Minor application framerate bugfixing.
Fix user representation assignment bug for is_inside_frustum.
Reduce virtual navigations of a PortalCamera to one.
Adjust vr_lab_rear_separate.py in order to allow tool visibilities in portal.