Editor: Instance editing mode - scale sub mode
Scale selected instance with primary/secondary edit drags. See the tooltip of the scale sub-mode for details.
Drag originating on one of the selected instances should scale the objects along all axis.
Additionally while in move mode selected instances should have a marker rendered on top of them (see red/green/blue arrows in screenshot, taken from blender). The arrows should be aligned to the coordinate systems defined by the selected instances. Drags that originate on one of the markers should scale the instances along the axis defined by this marker exclusively. Note: OpenMW does not support axis-specific scaling currently. All scaling is done uniformly. But we will add this feature eventually. It is up to the implementer, if he wishes to leave out the UI for per axis scaling for now or implement it but make it scale the instance uniformly for now.
Note: This task requires a properly working camera to be implemented first.
(RM-3167 from redmine: created on 2016-01-26 by Marc Zinnschlag, , closed on 2016-08-18 by Kyle Cooley, relates #3000 (closed), relates #3245 (closed))