Hello:
AFAIK, FSX Scenery objects placed via XML methods will not function as "Autogen" (
ex: with seasonal texture changes, batch rendering within 2 kilometers of the aircraft etc.) ...unless they are placed via the
FSX SDK Autogen 'Annotator' utility.
If one does
not need one's custom scenery objects to display with true "Autogen" characteristics, one can place them as a line of objects along a vector line (with or without randomization by type, size, heading, offset etc.) using
FenceBuilder Pro from FSAddon.
http://silvercloud-store.com/index.php?dispatch=products.view&product_id=29780
http://secure.simmarket.com/fsaddon-fencebuilder-pro.phtml
Alternatively one could use
Instant Scenery version 2 (aka "IS2", also payware)
from Flight1:
http://www.flight1.com/products.asp?product=instscen2
...or
SBuilderX (freeware when used for free add-ons.)
http://www.fsdeveloper.com/forum/downloads.php?do=file&id=72
Depending on what texture file type one uses and how the materials are applied, if one creates a custom FS9 scenery object instead of an FSX object, one could still place it and be able to display it in FSX by using
Scruffyduck's Scenery Design Editor (aka "SDE") which comes with the original
Library Object Manager (aka "LOM") for FS9... to place objects along lines
or within a defined polygon area, with some randomization options (freeware).
However, if you do need true FSX custom "Autogen" placed along vectors, IIUC, you would have to create a custom definition for that line in FSX Terrain.Cfg, in the FSX Default.XML file, and also in the utility used to generate a
CVX vector placement BGL file compiled via FSX SDK SHP2VEC ...in order for FSX to access and use them.
For info on what's involved in working with custom "Autogen" lines, search FSDeveloper and/or AVSIM Scenery forums.
...And see:
http://www.fsdeveloper.com/forum/showthread.php?t=23197&highlight=shores
...Also see this excellent and authoritative
tutorial by Luis Feliz-Tirado "Fun With Lines" :
http://forums1.avsim.net/index.php?autocom=tutorials&article=14
Hope this helps !
GaryGB