Maybe I'm missing what you're saying Gypsybaron. The first part, "mdl files are used to create bgl files", yep, very true, I've made some simple 3D objects in FSDS as mdl files and then converted those to bgl files to use as scenery objects.
Now by placement tool, I'm assuming you mean one like Instant Scenery, that is a placement tool. If so, then I would have to say, no, it doesn't require the mdl file any longer. Aside from the ones listed in that one image I posted at the beginning I don't have mdl files in any other scenery object libraries.
I've never used Instant Scenery however any tool that places scenery
is going to be creating a NEW BGL that contains the NEW
location parameters.
The tool may make use of GUID's which reference MDL's
and thus may seem to the user that no MDL file is used.
Once you have an object placement tool such as Instant Scenery, the mdl files job is done. All the placement tool requires is the bgl file. The bgl file is placed to a set of coordinates by the individual using the placement tool, the coordinates are not hardcoded into the bgl file by the original creator as you seem to be suggesting. If that were true, Object placement tools such as Instant Scenery would be useless since we could only place a bgl file where the original creator of that object wanted it placed by virtue of the lat/long he built into it.
As I indicated above, I believe that if any placement tool is using
a BGL as input, it is then decompiling that BGL, inserting NEW
location parameters and then creating a NEW BGL.
The location information MUST be hardcoded into the BGL that
is placed in a "scenery" folder, otherwise FSX ( of FS9 ) would
not know where to put the objects(s).
Here is an example of the intermediate stage of object placement
using ADE. It is in the XML file:
<SceneryObject
lat="53.5084943845868"
lon="8.05175319314003"
alt="0.0M"
altitudeIsAgl="TRUE"
pitch="0"
bank="0"
heading="112.988891601563"
imageComplexity="VERY_SPARSE">
<LibraryObject
name="{88d34df2-94ba-4068-a5a0-59609aeecade}"
scale="1.00"
/>
</SceneryObject>
Note the reference to the "LibraryObject". The GUID will point
to the objects MDL for insertion into the new BGL that ADE
will create to place that object at the location stated in
the XML file.
The XML file gets run through the XML2BGL utility to create
the new BGL. This process, again, may be totally transparent
to the user.
The point of the initial discusion was the need/use of the
MDL file that is often included in addon scenery. It is there
for the user to reposition the object using an approach like the XML to BGL tools.
If a tool like RWY12 is used the objects may be contained in
BGL libraries but when they are placed a new BGL is created
from information retrieved from the library BGL file. That
information would include the MDL data.
Paul