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MSFS20 MCX Fails to read MDLs in Asobo_Props.BGL

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GaryGB

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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 to MCX, this BGL takes quite some time to complete the import of 1,178 objects.


When imported to MCX, MCX event log reports:

"BGLX Reader failed to read MDL object from MDL file" for ~29 objects

...and MCX set to "Realtime" process priority, after ~an hour of elapsed time ...does not yet preview a 3D model.


IIUC, this coincided with Cleaning / Removing Triangles in MSFS 'default' files (which AFAIK, would already have "optimized" 3D geometry). :scratchch


To test this, I set MCX Menu > Options > {Processing} tab:

* Collapse ModelParts (un-checked)

...and:

* Small Triangle Threshold Limit (Meters Square) = 0.000000001000 = 1/1000 square mm (default value = 1/100 square mm)

...and MCX set to "Realtime" process priority, after ~an hour of elapsed time does not yet preview a 3D model.


[EDITED]

FYI: An older / larger 1,577,536 KB version of that Asobo_Props.BGL from September 2, 2020 does render to a 3D preview with 862 objects.

To date, MSFS 2020 used (5) versions of that filename.


As to MCX "BGLX Reader failed to read MDL object from MDL file" for ~29 objects Event Log entry, how do we find out "which" MDLs ? :oops:

[END_EDIT]


I am curious as to what you see, when you attempt to import this BGL ? o_O


PS: While searching for answers on a related possibility to explain the failure to change Cleaning / Removing Triangles with MDLs, I saw this:

https://www.fsdeveloper.com/forum/threads/can-mcx-recover-a-fsds-model.398206/

arno said:
Setting collapse parts to false only works when import a FSC file, when importing a MDL file it makes no difference since the parts are not in that format.

I would have to check what is going on with animated parts being rotated. Felix, do you also see that when you load the FSC file back into MCX or only in FSDS?
Click to expand...


That thread raises questions about functionality of MCX for MDLs versus FSC objects.

Perhaps the subject of your reply was to Felix' statement that: some parts are "grouped" ?


I use a lot of "Grouped" parts in my Sketchup 3D models.

Does this have any bearing on MCX import of "Grouped" parts in Sketchup 3D models ?

I would like to know, as I am planning a workflow for MSFS involving "Grouped" parts in Sketchup 3D models to make SimPropContainers.


Would you please clarify whether we currently can- or can not- control these options for processing of 3D MDLs (glTF's) imported by MCX.

Thanks in advance. :)

GaryGB
 
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Hi Gary,

You do realize that the BGL file you mention is about 1.2 GB in size (which is quite ridiculous for a BGL file containing objects). So I think this huge file size is enough to explain why the loading takes quite some time.

The quickest way to disable removing triangles is to set the small triangle limit setting to 0. But even for MDL files it makes sense to clean up, as they often contain small triangles without any area. The XtoMDL (or MSFS compiler) tool does not enforce that.

Disabling collapse modelparts has no effect on importing MDL files, as in the MDL file triangles are already grouped per part (material). When importing from SCASM files or FSC files this option controls if different model parts with the same material and other properties should be combined in one modelpart or not. But it has nothing to do with the clean up of the model (removing small triangles and such).
 
I do recognize that a larger ModelLIb type BGL with multiple MSFS Materials on some / all objects may require extended processing time. ;)

MCX has been importing ~5 hours with RealTime process priority in Windows Task Manager, but IIUC, it is still not finished processing that BGL.


How long might MCX require to process it on a 4.77 GHz 8-core CPU with 128 GB system RAM and ~ 1 TB of Paging file space allocated ? :coffee:


I am concerned that we may have run into another undocumented 3D library format change by Asobo since that file size / date has changed.


Are you able to complete an MCX import of the current Asobo_Props.BGL ?



Thanks for clarification on MCX' actual functionality, as I do not recall seeing documentation previously that MCX limits Collapse ModelParts to SCASM and FSC 3D models, but it does not work for MDL files. :pushpin:

If I experiment with importing 3D models having multiple layers of mapped Materials in Sketchup, I may wish to disable Collapse ModelParts.


We found that necessary for Ken Manning when working in Sketchup with MCX exports of FSDT KDFW ground markings on G-Polys in FS2Kx.

https://www.google.com/search?q=site:+https://www.fsdeveloper.com+GaryGB+kmanning+FSDT+KDFW+Collapse+ModelPart&client=firefox-b-1-d&hs=sHSp&sca_esv=1bcc83798a3a8aeb&ei=YFKnacPnAsX-ptQPxLbGwAg&biw=1200&bih=586&ved=0ahUKEwjDl8iF1oSTAxVFv4kEHUSbEYgQ4dUDCBE&uact=5&oq=site:+https://www.fsdeveloper.com+GaryGB+kmanning+FSDT+KDFW+Collapse+ModelPart&gs_lp=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&sclient=gws-wiz-serp

IIRC, MCX Collapse ModelParts can result in loss of content when a G-Poly's Materials are consolidated onto the same texture atlas sheet.


Thanks as well, for being "proactive" in reducing 'invisible' geometry details developers (both 3D modelers / Asobo) left in default 3D models.


As to MCX' cleaning / reduction of triangles, I was simply hoping to be successful in completing MCX import of the current Asobo_Props.BGL.


Thanks again. :)


UPDATE: After 14 Hours processing time, MCX has either frozen or otherwise has not completed its task importing Asobo_Props.BGL.


I wonder what SysInternals' Process Monitor might reveal when MCX does not seem to be doing anything after a while. :stirthepo

https://learn.microsoft.com/en-us/sysinternals/downloads/procmon


I found its predecessor "ProcMon" quite informative decades ago when we were baffled by some of FSX RTM's behavior. :scratchch


GaryGB
 
Last edited:
Hi,

I haven't had the time yet to test if that BGL file imports fine on my side. I just saw that it took a minute or two to get halfway reading the content and from what you describe it is the optimisation later on that takes most time.

If your parts already have different materials then disable the collapse model parts has no effect. It is only when materials are the same that different parts can be collapsed into each other.

Also running the drawcall minimizer will not collapse parts automatically. It will assign them the same texture, but if other material properties are different (e.g. the zbias value) they will still not collapse into one part.
 
Hi Arno:

MCX February 20, 2026 and March 3. 2026 builds both do not display any of the 1,178 objects imported from the above cited MSFS 2020 BGL, and both do not read 29 of the 3D models in that BGL.

While MCX shows activity during initial import, it does not show activity after a minute or so according to SysInternals Process Monitor.


The MCX task merely persists on screen, but apparently does not proceed past a certain point in the import process.

Windows Task Manager and SysInternals Process Explorer does not indicate that the ModelConverterX.exe process is 'not responding'.

I look forward to the results of your troubleshooting with future builds of MCX to ensure full functionality importing MSFS 3D models.

GaryGB
 
Last edited:
Did you check if version 1.8 can load the file?

I haven't really changed the MSFS MDL import recently, so I would not expect it to go broken due to a change.
 
Hi Arno:

That was a good testing idea I had not yet considered in my efforts to view what IIUC, was the MSFS 2020 latest version of Asobo_props.bgl.


I just used MCX March 23, 2025, and January 13, 2026 versions on the above cited latest Asobo_props.bgl version for MSFS 2020.

Both those versions processed Asobo_props.bgl in ~2 minutes, imported 1,207 objects, and rendered the first 3D model in MCX' preview pane.

There was no "BGLX Reader failed to read MDL object from MDL file" messages for ~29 objects during processing by those MCX versions. :)


MCX January 24, 2026 version shows the same processing issues reported above for latter February 20, 2026 and March 3, 2026 versions.


Thanks again for looking into this. :wizard:

GaryGB
 
Last edited:
Thanks Gary for testing. so then it seems it must have been a change between 13 and 24 January. That narrows down the scope quite a lot. I will check which changes in that period cause this bug. I hope to find time to look at that somewhere this weekend.
 
I have found out that it was the merge request where support to read skin and bone animations from MSFS objects was added that introduced the issue. Now let me figure out which bit of the change caused it.
 
I have found both bugs. One caused some MDL files not to be loaded and the other was an endless loop when optimizing the bones in the scenegraph structure. I hope to put the fix online later today.
 
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