I am referring to this dialog (from the manual). "Local elevation, Full visibility" is the only option available. Selecting "Generate FS8-Style GPs" seems to have no effect. The explanation from the manual for the "Local elevation" option is this:
"compiles all ground poly objects using the elevation of the ground for reference. This is the default for P3Dv3 and for FSX when materials have been used. For other situations, if the ground poly objects are at other than ARP elevation, use this option."
I am finding that, in nearly all cases, the ground elevation is not the same as the ARP in P3D where a fresh/no-addon installation has airports on plateaus due to flattening.
The next part of the ADE_GP manual that is useful is this part:
"for P3Dv3+ and FSX using materials – a model (.mdl) file is created for each GP object which is saved to a subfolder named ADE_GP in your ADE folder and a .xml file to position each of the models is saved to a file named ADE_GP.xml in your ADE folder prior to being submitted to the compiler in the SDK. The resulting compiled .bgl files named as the source .ad4 file suffixed with “_GP” and associated textures are saved as noted above."
With the latest SDK, there is something about this process that is probably causing these GPs to "stick" to the earth below the airport. I think the GPs are there, but are buried; your observations about having to slew high above to see your GPs gives some support to this hunch. Other threads here give me the impression that the GUIDs for some terrain features have changed in the latest SDK (Prepar3D v5 SDK 5.3.17.28160) and I am not certain that ADE is incorporating these changes. ADE for anything FSX/P3D related seems frozen in time since Summer of 2020, which is about when the world shifted attention to MSFS. Whereas the GP features have been updated several times, ADE has not. I am afraid what we may be experiencing is the slow decay when tools are kept in synch with each other. For instance, Arno's tools seem to be maintained, whereas the ADE tools are less so. Of course, these are all freeware gifts, so I am making observations and not complaints. The only option I had available to me to support ADE was to have purchased the ProKey, which I did. It seems that once the ProKey was discontinued, my suspicion told me that supporting the tooling for FSX/P3D was likely being deprioritized. Such is the way of things.
For these reasons, I am starting to pay closer attention to the SDK tooling and I am realizing that I might find better long-term sustainability for P3D if I just shift to a GIS-oriented solution as I am convinced that this is how the base scenery is made (hence tools like Shp2Vec). I am starting to think that a tool like qgis, particularly because it is very easy to extend with Python, might be a good solution. I can't easily replicate the features of ADE_GP as it does seem to build MDLs around flat surfaces, but I can create most of the inputs to the scenery tools with something like qgis.
With that said, I am happy to try out any combination of steps that might lead to a solution. I am literally on a default install with no scenery other than the one I am testing. Jyarddog, I have another post where I included my test scenery, and maybe you could post your .ad4 file here? If somebody can make your example (or my own, work), then we might have an opportunity to trouble-shoot.