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MCX Fails to read MDLs in "RJER_ModelLib.BGL".

F

FSullivan

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australia
Hi Arno...
first of all, thanks for enabling my account manually.

I think this will be very similar to thread:
G

MSFS20 Thread 'MCX Fails to read MDLs in Asobo_Props.BGL'

Hi Arno:

While replying to an inquiry in this thread:

https://www.fsdeveloper.com/forum/t...ial-normal_dx-or-normal_gl.460705/post-938912

...I discovered a potential issue with the current build of MCX.


The MCX version in question is:

MCX DevRel 1.9x dated Feb. 20, 2026


The MSFS 2020 BGL File in question is:

C:\Users\[user_profile_name]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages\Official\OneStore\fs-base\scenery\Global\Asobo_Props\Asobo_Props.BGL


NOTE: When imported...

The MSFS 2020 BGL file in question is:
"RJER_ModelLib.BGL" from MSFS2020 1.39.12.0(Steam edition), where I was trying to use an object from that file to a personal project.

When imported with MCX 1.8.251004-devrel(2025/10/04) there are no errors and 57 objects are imported.
When imported with newer MCX 1.8.2025.1221(2025/12/21) I have the message "Failed to read MDL object from BGL file" for 6 objects, and then nothing is imported.
When imported with newer MCX 1.9.2026.0512-devrel(2026/05/12) I have the message "Failed to read MDL object from BGL file" for 6 objects, and then nothing is imported.

I think this must be related with the issues found on the thread referred above.

Thanks in advance.
 
Thanks for reporting, I'll have a look. If it was exactly the same as the other thread it should have been fixed in the latest development release, so seems to be a different issue.
 
Hi Arno:

I did a search on my MSFS 2020 and MSFS 2024 installations and find no such "RJER_ModelLib.BGL" cited by the OP.

Perhaps this is a 3rd party BGL from another add-on ?

[EDITED]

Google states it is a 3rd party BGL:

https://www.google.com/search?q="RJER_ModelLib"+Steam&client=firefox-b-1-m&hs=5X2p&sca_esv=92bb7c0feee8c152&biw=77&bih=151&ei=lO8marL_H9u2mLQP8LGMiQc&oq="RJER_ModelLib"+Steam&gs_lp=EhNtb2JpbGUtZ3dzLXdpei1zZXJwIhUiUkpFUl9Nb2RlbExpYiIgU3RlYW0yBRAhGKABMgUQIRigATIFECEYoAEyBRAhGKABSJMvUNsNWMgqcAB4AJABAJgBwQKgAeIQqgEFMi0xLja4AQPIAQD4AQGYAgegAskRwgIIEAAY7wUYsAPCAgsQABiABBiiBBiwA8ICBRAAGO8FwgIIEAAYgAQYogTCAgUQIRirApgDAIgGAZAGBZIHBTItMS42oAfuELIHBTItMS42uAfJEcIHBTItMi41yAdOgAgB&sclient=mobile-gws-wiz-serp#lfId=ChxjMe

[END_EDIT]

UPDATE:

I checked the flightsim.to add-on that Google cited, and it did not contain the BGL file in question, but stated it utilized default MSFS 2020 assets..

I did not previously install MSFS 2020 - World Update I: Japan - By Microsoft in either MSFS 2020 or MSFS 2024.

After installing MSFS 2020 - World Update I: Japan - By Microsoft on my FS computer, I found the "RJER_ModelLib.BGL" cited by the OP.


On my FS development computer, MCX version dated May 3, 2026 (v1.9.2026.0503) was able to process all 57 of the 3D models in that BGL, and generate 3D previews.


Perhaps the OP may need to use a more recent "Development" release of MCX that has actually been updated by Arno ? :scratchch

https://www.scenerydesign.org/development-releases/

https://www.scenerydesign.org/latest-release/modelconverterx_latest_development_release.zip


To test this, I installed and tested MCX v1.9.2026.0512, which was also able to process all 57 of the 3D models in that BGL, and generate 3D previews.


FYI: Both MCX versions cited above work OK with MSFS files I processed (many thanks again for that update, Arno. :wizard: )

That said, my MSFS versions are from the Microsoft Store, and the OP's MSFS version originates via STEAM; might this be an explanation ? :idea:

GaryGB
 
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Thanks Gary for checking. Since you can load the BGL file with the current development release, I would suggest that @FSullivan first try to see if the latest development release works on his machine as well.
 
Hi Arno...
as stated on my initial post:
MSFS2020 1.39.12.0(Steam edition) with both "World Update I: Japan" and "World Update 20: Japan".
When imported with MCX 1.8.251004-devrel(2025/10/04) there are no errors and 57 objects are imported.
When imported with newer MCX 1.8.2025.1221(2025/12/21) I have the message "Failed to read MDL object from BGL file" for 6 objects, and then nothing is imported.
When imported with newer MCX 1.9.2026.0512-devrel(2026/05/12) I have the message "Failed to read MDL object from BGL file" for 6 objects, and then nothing is imported.

I have been able to go with my project using MCX 1.8.251004-devrel(2025/10/04) as stated above, and not with the newer ones, which is weird.

FSullivan
 
So, both Gary and you use the same 1.9 release (the latest one) and on Gary's machine it loads but on yours not. I guess I need to install the world update and see what happens on my machine.
 
Hi Arno...
I already discovered what the issue is, but I don't understand why MCX 1.8.251004 is not affected, so there have been some changes in MCX on the newest versions that makes the issue show up.
The issue is caused by an invalid link (from "MSFS Addon Linker") in the MSFS community folder.
For example:
If "my-project" folder is linked with "MSFS Addon Linker" to the MSFS community folder, there are no issues with MCX (the three versions referred above) reading the "RJER_ModelLib.BGL" file.
Now, if I delete or rename the "my-project" folder, the link on the MSFS community folder become invalid and then the MCX (just the two newer versions referred above) shows the issue - "Failed to read MDL object from BGL file" for 6 objects, and then nothing is imported.
Please, note that with MCX 1.8.251004-devrel(2025/10/04) there are no issues, even with the invalid link provoked above, which have lead me to all this confusion.
This invalid link behavior, is very common for me, since during personal project testing, I just remove the "my-project" folder without touching the "MSFS Addon Linker", leading to the invalid link situation.
May be this can be addressed, to make the newer MCX versions handle like the older MCX 1.8.251004, in this respect.
I hope being helpful.

FSullivan
 
I had planned to test this Symbolic Link related behavior with some add-ons when MCX attempted to process certain BGLs.

FYI: I use Link Shell Extension to create "Symbolic Link Clones" as 0-byte virtual shortcuts to original linked physical files and folders.

https://www.google.com/search?client=firefox-b-1-m&q=Schinagl+Link+Shell+Extension#lfId=ChxjMe

I have seen some instances comparable to that of the OP with MCX when attempting to process Symbolic Link Clones.

When MSFS Add-on Package folder chains are linked to the MSFS Community folder, most (...but not all) such add-ons work OK at run time in MSFS.

However, results are variable with MCX when attempting to read and process BGL files, and I now make a point of directing MCX to work only with original physical file and folder chains in my un-ZIP-ped / un-RAR-ed sources that I link to the MSFS Community folder.

I have previously seen situations where MCX failed to access files intended to be processed, even when run as Administrator, if Windows Security attributes did not permit the current logged user access via system Properties for specified files / folders.

Hopefully this info might prove useful for Arno to optimize features and accessibility in MCX for the future.

GaryGB
 
Hi Gary...
note that the invalid link behavior explained above in "MSFS\Community" folder, apparently have nothing to do with the file being read "RJER_ModelLib.BGL" that is on "MSFS\Official\Steam" folder, and this issue just showed up on the most recent MCX versions.
Very weird situation.

FSullivan
 
Hi,

What does the MSFS addon linker do? I'm not familiar with that.

A difference between version 1.8 and the development release is that I have added support for reading livery packages that reference other packages for the geometry. Although that would normally only apply to aircraft models, so not sure if it affects BGL files as well.
 
MSFS Addon Linker (authored by "Bad2000") basically creates a Symbolic Link between physical files / folders for MSFS add-ons in a 'source' folder, and the MSFS Community folder "Virtual File System" path ...then enables / disables them via a custom folder tree-type checkbox GUI.

https://flightsim.to/addon/1572/msfs-addons-linker


I manually do that with Link Shell Extension, which after installation to the Windows Explorer File Manager shell context menu system, allows one to select source file / folders via "Pick Link Source", then drop them on a target path folder via "Drop As" links; ("Symbolic Link Clones" as 0-byte shortcut icon placeholder shortcuts, which thus far works as the best link type for my purposes).

BTW: Mark Russinovich of WinTernals / SysInternals (now c/o Microsoft) has a utility that can work with Symbolic Links and Junctions via command line methods ;-)

Hope this helps a bit more.

GaryGB
 
Last edited:
But given that this is a default scenery package that is part of the official and not the community folder, I don't understand why you would want to use a symbolic link for it.
 
Personally, I do plan to test use of linking default content eventually when I get time to do so.

Although MSFS 2020 Content Manager is an option, I prefer manual control over all that loads into MSFS.

So for packages such as Japan where I do not routinely fly or develop, I may consider imposing load control via a link.


I find that reducing the total volume of content that FS indexes and loads ...impacts both SDK DevMode and FS run time performance. ;)


For FSX, I use Scenery Config Manager, which is somewhat comparable (albeit for an earlier FS version):

https://fs-sceditor.sourceforge.net/


In FS2002 and earlier, I also used comparable utilities to reduce FS' total volume of content indexed and loaded.

In only rare cases, one may find dependencies that must be re-enabled as they are used elsewhere in the FS world.


I am especially interested in testing the limits of disabling default content outside FS world areas I work in / fly in ...to optimize FPS.

This becomes a consideration for folks like me who keep FS Terrain LOD set to its maximum ...at all times.


BTW: I do not have MSFS Addon Linker installed, so perhaps the OP can tell us if by default it links "Official" content ?

GaryGB
 
Last edited:
There is a big confusion here. I never said I created a symbolic link to "RJER_ModelLib.BGL" and the issue is not with this file (could be anyone).
I will put this in other way:

Any BGL files on "MSFS\Official\Steam" (physically untouched ones) can not be read by the recent MCX versions, if there is an invalid link (for whatever reason) on "MSFS\Community" folder, that's it.

I see no reason why an invalid link in "MSFS\Community" can lead for MCX (newer versions) to not read any BGL file (physically untouched ones) on "MSFS\Official\Steam" folder.
And no, I am not linking "Official" content (but I could).
The invalid links I said, are provoked by me during my projects process and are occasionally on "MSFS\Community" folder and not on "MSFS\Official\Steam", from where MCX (newer versions) should read their BGL files with no issues.

Please, note that this is not a big issue, since I have now discovered their cause, but I have raised the post, just to let you know this is happening, since I think there is no reason for MCX (newer versions) to fail with this behavior.

FSullivan
 
HI Frank:

The MSFS Community folder is intended to only contain links to- / or actual stand-alone- physical folder chains of compiled "Packages".

AFAIK, MSFS Community folder should not be directly linked to a ex: MyFSProjects\Packages folder chain (this is done internally via SDK DevMode c/o MSFS Virtual File System).

Perhaps Arno may reply as to how / why MCX (sometimes ?) reads only physical files and ignores system paths to such files made accessible via Symbolic Links ?

GaryGB
 
The invalid links are occasionally provoked from personal compiled "Packages", when for any reason the source was deleted or renamed. But this is not the discussion.
Again:
Any BGL files on "MSFS\Official\Steam" (physically untouched ones) can not be read by the recent MCX versions, if there is an invalid link (for whatever reason) on "MSFS\Community" folder.

FSullivan
 
The MSFS Virtual File System (aka "VFS") is explained in the following query result:

https://www.google.com/search?q=MSF...8cUwgcJMi0xLjEwLjE0yAfEA4AIAQ&sclient=gws-wiz


AFAIK, if you use STEAM, your STEAM-specific MSFS "Official" and "Community" paths are explained in the following query results:

https://www.google.com/search?q="MSFS\Official\Steam"+&sca_esv=3b4cc2d9bc5e80fb&source=hp&ei=JukpavatOK_druEP5aLI0Qw&iflsig=AFdpzrgAAAAAain3NpsqZDmH98RQ71kFawJoHe9Tdy3R&ved=0ahUKEwj22PiO4P2UAxWvrisGHWURMsoQ4dUDCB0&uact=5&oq="MSFS\Official\Steam"+&gs_lp=Egdnd3Mtd2l6IhYiTVNGU1xPZmZpY2lhbFxTdGVhbSIgMgUQIRigATIFECEYoAEyBRAhGKABMgUQIRigATIFECEYoAEyBRAhGKsCMgUQIRirAjIFECEYqwJI5hhQAFgAcAB4AJABAJgBcKABcKoBAzAuMbgBA8gBAPgBAvgBAZgCAaAChQGYAwCSBwMwLjGgB5kFsgcDMC4xuAeFAcIHAzMtMcgHD4AIAQ&sclient=gws-wiz


AFAIK, if you do NOT use STEAM, your specified MSFS "Official" and "Community" paths are explained in the following query results:

https://www.google.com/search?q=MSF...ji4B7oQwgcGMy0xOS4zyAeTAoAIAQ&sclient=gws-wiz


IIUC, your work flow creating links at any time / for any purpose to a non-STEAM "Community" path may confuse both STEAM MSFS VFS and MCX.

It is my impression that MCX is working as intended, and broken links corrupt MSFS VFS info MCX reads, so this occurs through no fault of its own.


There are other recommended work flows to optimize use of MSFS SDK DevMode and Compiled Packages etc. that should IMHO be used instead. ;)


Rhumbaflappy (aka "Dick Ludowise") and others here use MSFS STEAM edition; perhaps they may offer more suggestions to help optimize SDK use ?


Please link to a ZIP of a example MSFS project, and explain what you seek to achieve via your use of "MSFS\Community" folder links in MSFS-STEAM.


PS: If you are attempting to use links to Packages for optimizing SDK DevMode GUI performance, you may wish to review this thread: :idea:

https://www.fsdeveloper.com/forum/threads/lag-and-freeze-in-developer-mode.453549/



GaryGB
 
Last edited:
Gary, will all respect I thank you all the efforts in pointing me all that links, but all of them just only have knowledges that I know from long ago.
Please, if you have enough patience, follow the steps below (now, I will use "Link Shell Extension" to show that this behavior have nothing to do with "MSFS AddonLinker"):

1) Create just an empty folder where ever you like and name it "TEST".
2) Create a symbolic link with your "Link Shell Extension" of folder "TEST" on your MSFS community folder.
3) Use MCX latest version and import "asobo-airport-biis-isafjordur\scenery\isafjordur\Isafjordur.BGL" (this is for sure an official MSFS library file).
You will see that all 10 object models will load with no issues.
4) Close MCX.
5) Now, delete or rename the folder "TEST" you have created in step 1. (*)
6) Use MCX to import the same library file, as in step 3.
Now you will see that MCX have error messages (Failed to read MDL object from BGL file) and nothing is imported.

This is what I am trying to demonstrate from the beginning, and this is the best I can do to report what I have found.
(*) Well, you can say that I can not do step 5, but that is not we are discussing.
I continue thinking that there is no reason for MCX to fail because of this behavior (older MCX versions can handle this same behavior, with no issues).
Sorry, but I only want to contribute to make MCX even better and error free.

FSullivan
 
Hello:

I have followed your instructions above using Link Shell Extension and MCX May 12. 2026 version 1.9.2026.0512.

MCX is able to process the specified BGL normally both with- and without- an intact \Test folder Symbolic Link Clone.


IIUC, something is configured differently on your Windows installation of MSFS and/or MCX ...compared to mine. :scratchch


FYI: I also have no trace of either FSX- / MSFS- / other versions of Steam installed anywhere on my computer.


To check if Windows Security permissions are a factor you may try running MCX with 'Trusted Installer' permissions:

https://www.google.com/search?q=Win...wZwgcHMC4yMS4xNcgHYoAIAQ&sclient=gws-wiz-serp

NOTE: Use that utility with extreme caution and precision; disable it when testing is finished.


AFAIK, Arno may be testing this scenario as we speak; if not, it would seem reasonable that he reply here eventually.

GaryGB
 
Gary...
have you done step 4 ?
You must close MCX, before continuing to step 5 and 6, otherwise MCX will not fail (maybe because have the read data still in cache).

FSullivan
 
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