Hello:
Did you make a separate airport background flatten BGL in ADE9X or another FSX SDK compliant utility ?
Most airfield developers make a flatten for the airport background (the 3-attribute type most of us make)... which assigns the GUID for:
"
Airport_Backgrounds_Flatten_MaskClassMap_ExcludeAutoGen {46BFB3BD-CE68-418E-8112-FEBA17428ACE}"
This would effectively exclude all autogen underneath the area of the flatten polygon.
BTW: That flatten BGL should be located in an active \Scenery folder "in or above" the FS scenery library area layer that contains the custom photoreal legacy tile bitmaps or FSX compressed quad matrix photoreal imagery BGL and *.AGN files in the \Texture folder.
Alternatively, you can use smaller FSX SDK CVX Vector "Exclude Polygons" to eliminate only certain individual or grouped trees on your airfield to preserve autogen in areas which you find the autogen "pop-ups" acceptable.
FYI: Custom autogen in *.AGN files for use with custom photoreal scenery textures (ex: UK-VFR, Horizon GenX scenery etc.) is treated by FSX as a type of vector entity or object.
"Excluding" an autogen vector object from being displayed in FSX merely requires an "Exclude Polygon" that has the proper GUID attribute.
That "Exclude" for
FSX autogen "vector objects" must itself be a vector
polygon type BGL created with FSX SDK SHP2VEC, and NOT the legacy "Exclude Rectangle" type for "scenery objects" created with XML and BGLComp (...which is indeed what we otherwise use to exclude autogen in
FS9).
A description of how to make a Vector Polygon for autogen exclusion in ADE9X is in this thread:
http://www.fsdeveloper.com/forum/showthread.php?t=17999&highlight=polygon
NOTE: For a typical 3-attribute airport flatten, in the ADE9X "Add Polygon" mode "
Terrain Polygons" dialog, select "
Airport Background" and then in the "Tag" list pick "
Flatten Mask Class Map ExcludeAutoGen"; click OK
PS: If you also wish to blend the edges of the airport flatten into surrounding terrain, see this thread:
http://www.fsdeveloper.com/forum/showthread.php?t=17964&highlight=flatten
Hope this helps !
GaryGB