Here we take the runway as example.
The runway is composed of several layers-
Here we make it in 5 layers.
1. Base layer- seamless asphalt. This is for getting the tiny details and crispiness. This should be tessellated. (same size and width as the runway itself)
2. This will be another plane in gmax. This you can make in photoshop (or similar). You can also tessellate this. It will be a semi transparent wispy dark layer.- Thats for getting the overall color of the runway. Use as PNG for transparency. This also could be made from road textures.
3. Next is the runway markings.
In Gmax use curve tool and loft a plane through it. Then get the appropriate White and yellow runway markings texture. Run through the lofted plane.
4. Last layer is runway skidmarks. You can paint it in photoshop. Do not tessellate it. Make it as full length x width of runway.
5. Runway numbers. This could be your top most layer. Make two planes at each end of the runway and texture them with appropriate numbers.
Export everything to MCX as MDL.
In MCX, Open Ground Polygon Wizard. (This is because if you just place it normally, it will cast shadows of itself and runway is a ground plane. Not an object)
-Click the box right to 'select file to convert'.
You will see all your runway objects in 3D.
Now under 'Layer' start with layer 12. (this will put everything on top of default FSX layers)
Then build up your layers in ascending values.
Now its time to find the position of the runway in the world.
Under position, find your runway's 'lat' and 'lon' (latitude and longitude). Use either google maps or FSX itself. Make sure its in decimal form.
Find your runway's heading and altitude- type them in.
Click convert. And run FSX.
Make sure you put textures in its right folders.
Any questions? comment.