I'm going to open this can of worms again.
I've been playing around with terragear for quite a while, and most of my trials have hit walls. (the ole biting off more than I can chew problem). I think I have a pretty good handle on upgrading genapts to the 8.50 version, however. Most of the work can be done using the current .btg format if I preprocess the bezier curves. The only thing that would require updating .btg would be polygon offsets, to draw the line features 'above' pavement. I haven't gotten that far yet. I do have a parser handling the pavement types, and the beginnings of the taxiway stripe polys being offset from the edge.
Not seen in the screenshots is my bezier curve handling (my first attempt was brute force, and wrong). The 850 format can specify cubic and quadratic curves, and knots. I have the data in a format now that should allow me to produce accurate curves.
I'm also writing most of this with OSG, so I can see the progress as I go without loading it into flightgear. Eventually, I'll have to write out a .btg file
Here is a wireframe look at KATL:
I hope to have polygon-offset working in the next couple of days (in my viewer). The distance of the stripe to the pavement edge is currently constant from the vertices. This is incorrect, as it should remain constant distance from the edge of the pavement.
Next, I'll add back the bezier subdivisions, then comes texturing.