LOD Blender object creation: does this process makes sense?

[vbazillio]

I'm a beginner in Blender (and 3D in general) as well as in MSFS scenery design. I have several small freeware sceneries with basic single LOD basic objects. I want to update these with multi LOD. I want to check with more experience developers that my workflow to create these multi LOD object makes sense. And obviously collect, your best advice.


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For the sake of explaining how I plan to update all my object, I’ll take a simple blue pole object for my San Diego Gillespie (KSEE) freeware.

1. BackUp my original most detailed object into a Collection name _LOD0-Original and Hide in Viewport.
2. Duplicate my original collection into a _LOD0 and merge all object into a single one.
3. Duplicate the LOD0 collection into LOD1 new collection. For this _LOD1, Add a Modifier - Decimate and manage the ratio to reduce (very) approximately to 1/4 the number of vertices, faces and Tris. Very approximately. This is where I need help to make something rational and… maybe smart.
4. Duplicate the _LOD1 to a new collection _LOD2 and again apply a Modifier - Decimate, and again reduce approximately. I may remove some texture - if needed - and replace it with basic color material for example.
5. Repeat Step 4 to _LOD3 and _LOD4.
6. Use the Blender free plugin LN LODs, click calculate “LOD Sizes” and click “Set LOD Values in Asobo Exporter”. It populates automatically the value for my Multi-Exporter gLTF 2.0 plug-in
   
   
   
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7. Export my object. Here I’m not sure at all that the LOD value makes sense LOD0 is 5, LOD1 is 3, LOD2 is 1 and LOD3 is 0. Shouldn’t it be the other way around ?

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Any tips & tricks are welcome. The export works fine and my object are visible in MSFS.The debug LOD doesn’t displays “logical” info with only the LOD0 loaded , here at short distance, big size in the screen:
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… and still LOD0/3 at far distance:



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Thank you for your help!

 

[rhumbaflappy]

Untick Force User LOD 0 ?

 

[vbazillio]

Untick Force User LOD 0 ?

Oh! Right! So obvious. I ticked/tested so much settings that I certainly forget this one. That's why it use to work and didn't work anymore with the Debug Tool. I will untick and validate. Thanks for the call.

Any advice regarding the flow process to generate the multiLODs object?

 

[rhumbaflappy]

https://docs.flightsimulator.com/ms...xtures/Modeling/LODs/LOD_Selection_System.htm
This contains all the info Asobo is sharing.
This is interesting:

Apparently, the sim can then decide the minsize.

This is the general guide. Asobo recommends using the High column. You could seek to make the vertex count similar for each LOD. And yes, you can use a huge invisible material cube to force display. Both Asobo and Microsoft do this. ModelConverterX has a very good LOD system if you want something automatic.

 

[vbazillio]

Untick Force User LOD 0 ?

After un-ticking "Force User LOD 0", thank you... All seems ok.

https://imgur.com/UvzE3e7

https://imgur.com/75znzln

... although I count 4 levels in my .XML. But I'm OK with that. And this pole is just for the sake of the demonstration and I think it doesn't required that amount of different LOD.

<?xml version="1.0" encoding="utf-8"?>
<ModelInfo guid="{02571d45-0398-4ae1-900e-3553045510c2}" version="1.1">
    <LODS>
        <LOD minSize="4" ModelFile="vbcorp-ksee-blue-poles_LOD0.gltf"/>
        <LOD minSize="3" ModelFile="vbcorp-ksee-blue-poles_LOD1.gltf"/>
        <LOD minSize="2" ModelFile="vbcorp-ksee-blue-poles_LOD2.gltf"/>
        <LOD minSize="1" ModelFile="vbcorp-ksee-blue-poles_LOD3.gltf"/>
    </LODS>
</ModelInfo>

 

[rhumbaflappy]

Some more thoughts about LODs in MSFS 2024 and Blender.

In Blender we often have Ngons and Quads the are part of out polygon makeup for out objects. But the glTF uses triangles only, and this is automatically taken care of in exporting. That leads to a difference in what Blender sees as face counts between the glTF and Blender. To get an accurate display of faces and verts, we need to import a gltf to Blender, which then accounts for the triangulation. Not really needed, but something to be aware of concerning LODs.

Also, a discussion of ideal LODs at Asobo's devsupport site, leads me to believe that LODs should ideally be quartered in decimation... not halved. Here's a small project that uses an icosphere to show quartering using the decimate modifier. LODTest.zip

The xml I used was:

<?xml version="1.0" encoding="utf-8"?>
<ModelInfo guid="{c13afae3-819a-469d-b8f2-0b9b68724766}" version="1.1">
    <LODS>
        <LOD minSize="6" ModelFile="Icosphere_LOD0.gltf"/>
        <LOD minSize="5" ModelFile="Icosphere_LOD1.gltf"/>
        <LOD minSize="4" ModelFile="Icosphere_LOD2.gltf"/>
        <LOD minSize="3" ModelFile="Icosphere_LOD3.gltf"/>
        <LOD minSize="2" ModelFile="Icosphere_LOD4.gltf"/>
        <LOD minSize="1" ModelFile="Icosphere_LOD5.gltf"/>
    </LODS>
</ModelInfo>

As per the SDK this lets the sim decide the minsize of each LOD. I just made duplicates of the LOD0, and decimated them. LOD1 was decimated at 0.25. LOD2 was decimated at 0.0625.... https://docs.flightsimulator.com/ms...xtures/Modeling/LODs/LOD_Selection_System.htm

The red warning tells me It shouldn't have a texture at the lowest LOD... probably didn't need one much earlier.