Would it be easy to split it up into 2 model XML files?
Yeah that would also work. I don't know if it would be easier to do that or ludomotico "hack".
What I really want to finish investigating is the "internal-shadow-control branch aircraft" I setup. All that is left to complete is the interior cockpit objects being duplicated in the model. Everything else "glass and windows" already is.
It will appear to be the cleanest looking as you'll only have one aircraft entry or name in fgrun and some menu choices. What I am really curious about is, what if any overhead there is in duplicating all those objects in the model?
Other than that, it is pure aesthetics from a programming perspective of resorting to that type of manipulation to get the compatibility regression. But if it doesn't negatively affect the current behavior of the aircraft, who cares?
I already committed the finalized internal cockpit object list and duplicated the objects in my local model, but I have something wrong. Bad child count or broken group. It was working with the glass and window duplicated but after I duplicated the 20+ some odd cockpit objects, I get a corrupted or missing fuselage when switching the internal shadow on. I'm pretty sure it is just a minor mistake somewhere in my duplication process of the model.
You know, there is yet another option. I don't know if I would recommend it for everyone, (I'd certainly try it if I was on 3.4). Thorsten kind of verified on the mailing list that there were no special core c++ edits to make the glass and shadow effects (internal) work in 3.5. So technically anyone using 3.4 could simply copy 3 shader files, one eff file and one xml file from 3.5 to 3.4 and should have the effects framework working.
I'm pretty sure this is all that was touched.
Shaders/glass-ALS.frag
Shaders/glass-ALS.vert
Shaders/model-interior-ALS-base.frag
Effects/glass.eff
Environment/environment.xml
I don't know about the "external" shadow-volume, if any core c++ was required or not. It would require a couple more files. But at least it is already accounted for even though it is by not using it.
WARNING:
If anyone wants to experiment with their 3.4 install to see if this works, make sure you backup any of those existing 3.4 files first and then just copy these five FG 3.5 files to FG 3.4.