It's a Display Layer Manager, similar to Photoshop's.
You can create containers to organize and manage groups of displayLayers, using drag and drop...
Installation:
- copy the script "hdl_UI.mel" into your scripts folder
ie. C:/Documents and Settings/Administrator/My Documents/maya/MayaVersion/scripts
- copy the "vlHdl" folder into your "prefsicons" folder
ie. C:/Documents and Settings/Administrator/My Documents/maya/MayaVersion/prefs/icons
- source the script or restart Maya
- enter the command: hdl_UI
Note: since HDL is meant to be an alternate displayLayerEditor I suggest to toggle off the internal Maya displayEditor via the "option" menu in the UI while using HDL. This will not harm Maya or your scene in any way (you can always reactivate it in the same menu).
Read the version history page here on highend for changes in this version
Feel free to send me feedback and, of course, bug reports!
Vincenzo