by Hooray » Sat Feb 20, 2016 7:53 pm
it is what it is, and being what it is (a set of external patches), it has a certain barrier to entry, and learning curve, associated with it.
Basically, people wanting to use this, will need to know how to build FlightGear from source, how to use git and how to apply patches.
People with a working build environment should have no problems getting this to work - the main caveat being currently that some recent sg/fg developments would not be integrated yet.
But otherwise, all the documentation that you can find on the wiki about building FlightGear from source, using git, will be applicable - the main difference is that once you have everything set up and working to build stock fgfs, you would add poweroftwo's gitlab branches as git remotes, and then build an older version of SimGear/FlightGear which contains the corresponding patches.
This was originally put up for review a few years ago, but many things happened in the meantime, such as gitorious shutdown, but also community turmoil revolving around the fgdata/fgaddon split, bad timing (release preparations), as well as a review process that ended up looking fairly tedious and stringent given the nature of the commits made by other core developments during the same timeframe - so that it is pretty safe to say that the integration of those patches got stalled, and that these osgEarth patches are currently only available to "power users" who are able to build from source.
To be fair, Curt did try to raise this again on the devel list a while back, but it seems pretty obvious that the latencies involved in getting such patches reviewed, discussed and integrated in a timely fashion may to be all that appealing for people who are not just volunteers doing this in their spare time.
Likewise, given the recent progress made in SimGear and FlightGear, it is also becoming more and more unlikely that those patches will apply cleanly, i.e. could be git-rebased easily - so that getting this integrated would require a fairly orchestrated effort among all the parties involved, as well as concessions by those doing the review/integration, which may not be as simple as it sounds, because a number of people have already spent considerable time on this, to no avail.
All this needs to be put into perspective, i.e. taking into account that this is a fairly substantial patch touching quite a few areas that are not actively maintained by other core developers, and that there's generally a shortage of active core developers - especially those handling merge requests and doing reviews. For the time being, Torsten, James and Stuart are the main people handling such things.
If, when and how this may be made available in the future, or even just picked up again by other core developers is up to others to decide - but I guess, your best bet is learning how to build FlightGear from source.