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Flatten- now you see me, now you don't

adr179

adr179

Resource contributor
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259
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slovenia
I came across an interesting problem: On an airport with sloped runway i have basically two scenery locations with objects, difference in altitude is 11 meters. Runway was made as a model in GMax, surrounding terrain is adjusted with sloping polys, objects scenery locations are flat within the same flatten bgl, there is an apron made in afcad on main airport elevation and another one under separate location that is higher.

All this conglomerate shows up just fine if flight is started on this airport, but if I fly to this airport from any other origin, regardless of distance, my objects are either burried into the ground or hang in the air, giving a feeling like flatten bgl is not loaded. Scenery layers are organised like this:
- objects scenery
- afcads
- flattens&excludes
- photoreal
- mesh

Any ideas?
 
Perhaps your excludes are the problem? (i.e. an exclude is excluding a flatten or one of your flattens is an exclude type?)

What codes/Guids did you use for your flattens and excludes?

Also, excludes only use the bounding box of the polygon so odd shapes may flatten areas that you don't want flattened....
 
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Unfortunatelly that is not the case, since I keep a strict order here. There are actually no mixed bgl files, so excludes are strictly kept within one bgl and flattens are placed in another bgl. For the particular area of this airport there were actualy no excludes needed, so I only have two flatten areas. In the mean time I also noticed that this problem actually only appears if I depart from two nearby airports. If I start my flight from any other airport that's further away, so distance from this problematic airport is greater than ~25NM, everthing is fine, flattens are there, all of the objects are in place.
 
Well, looks like I really discovered an issue with this. After extensive testing on three other computers it's all the same:
If you happen to have a scenery setup like mine is, then expect this kind of problem: your flatten bgl, for some reason won't get loaded properly if you start a flight at distance that is approx. 20 to 25NM to the destination, resulting in some extent of anomally of objects altitudes. If flight is started at origins grater than 25NM away or on airport itself, everything will be fine.
 
Timmo, I understand your pattern of thinking in previous post of yours. If any of your considerations would actually be correct, then this kind of error would and should manifest itself regardless of any condition and under all circumstances. At least that is something that one would logically expect and my conclusions are as described in previous post. But sometimes logic fails...
 
Is this a new airport, or a remake of a default airport? If a remake, what is the elevation of the default airport, and the elevation(s) of any "AFCAD" replacements.

scott s.
.
 
Sorry, I overlooked omission of this relevant fact. It's a non-default airport, so there's no interference from default scenery, at least as far as flattens and/or exclusions are concerned.
 
Hi there,

I wonder whether this is related to a similar issue that I have observed with terrain mesh and land class files: the normal/desired priority can become reversed when files have different spatial footprints and thus get loaded at different times during a flight. That means that starting a flight at location X would load all local files at once and FS sorts them correctly by priority, while flying to that same place from outside can mean that FS "sticks with" the file it loaded first and only a forced scenery refresh will re-establish the correct file priority.

The only "fix" I know for this is to ensure that the spatial footprint is identical for all "competing" files but that's usually impossible to achieve given that there's no standard for coverage area (even the default files don't all adhere to the same QMID extent).

You could experiment with adding "dummy" data in locations quite a ways away from your airport. These could be small terrain-hugging flattens (LandWaterMask_Land_NoFlatten) or something similar. The idea is to extend the spatial footprint of your file, as defined in the bgl header, which might help with the proper sequence of loading.

Then again, the issue could be something different altogether.

Cheers, Holger
 
Thank you for a suggestion, Holger.

I certainly will give it a try and (normally I'm not a
forecaster)I have a strong feeling, proposed solution will resolve this problem.
 
Problem solved. I placed another tiny flatten just north of my original location, but far enough for this new flatten to be in another QMID 13 quadrant (the two original flattens were in the same quadrant - it's a small airport) and everthing is now as it should be.
 
Hi there,

thanks for letting us know it worked. I never tried this myself in a specific test so it's great to hear of some hard evidence for this theory.

Cheers, Holger
 
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