MSFS20 FSPackageTool is changing my geometry (changing triangles and adding texture vertices) causing texture distortions. Major bug? [SOLVED]

[RicherSims]

TLDR: Models are changing after running through the FSPackageTool, causing textures to become misaligned. How can I avoid this?

Why this is even a thing I don't know, but it is happening.
This seems to be related to the following threads on texture distortion:

MSFS20 - Distorted texture

Some time ago I posted a thread in the MCX section of this forum about distorted textures. I was suggested to post about it in Sketchup. I was also advised to tke a look at Aerilius' Make Unique Texture++. But before I dive into that, can someone say what it does and how it would help...

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MSFS20 - Texture Distortion when Importing into MSFS

Hi all, I recently encountered a issue where the texture becomes squiggly when it's imported into MSFS. In Blender and Substance Painter, the texture look fine. Here are some photos for reference. MSFS: Blender: MSFS: Blender: UV Layout: In this case, I used smart uv project, in order to...

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MSFS20 - blurry-trembling, jagged, stretched, twisted, wavy texture maps in MSFS with custom ground poly as ProjectMesh

Hi all, Piece by piece I've been exporting my airport to MSFS via MCX export. Everything is normal so far except that I've been noticing jagged, wavy, and trembling textures in several areas of the ground poly and building ceiling textures. I wonder what can cause this? Textures seem to stretch...

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The posters in these threads all experience similar issues, but the important distinction is this happens no matter if your model comes from Sketchup, Blender or MCX. So I investigated further and compared my GLTF before and after it went through FSPackageTool and sure enough, the model texture vertices have changed.
Here are 3 example areas (left-side: before, right-side: after):

Spoiler

Spoiler

Spoiler

As you can see the number of triangles have increased from 28,157 to 28,196 and the texture vertices have increased from 41,769 to 43,028.
This causes misaligned textures which manifest as seams, jaggedness, crookedness and blurriness.
I can confirm that the textures themselves appear to remain unchanged.

These small distortions become unbearable, especially when the user will be up close (example near the gates of a terminal).

Even when the changes may not be always be visible on the surface of the model, the FSPackage tool seems to make changes even on small simple objects,
Another model had its number of triangles unchanged (745), but the number of texture verts did change (1151-> 1187).

This is a real headache.
How can I avoid this? Or better yet: can Asobo allow the FSPackageTool to process our models without changing them?

 

[rhumbaflappy]

Asobo only support exports from 3dsMax, so you're not likely to get help from them.

Quads or ngons are a problem in MSFS compilation. I believe all gltf mesh need to be in triangles. Also, I am unsure how the sim deals with double-sided materials, or how they get compiled.

 

[=rk=]

As you can see the number of triangles have increased from 28,157 to 28,196 and the texture vertices have increased from 41,769 to 43,028.
This causes misaligned textures which manifest as seams, jaggedness, crookedness and blurriness.
I can confirm that the textures themselves appear to remain unchanged.

You relate an increase of 39 triangles, to a "change in geometry," while ignoring the very obvious fact that 1,259 additional vertices, proves MCX accepts Sketchup multi-trigonal "polygons." No geometry changed, the MSFS compiler insists all polygons must have only three vertices, because it is mathematically impossible to construct a polygon with four or more coplanar vertices - despite what Sketchup rounds up to.

Everything you've described is a consequence of allowing UV offsets to increase beyond the zero/one range. It is a known limitation of the MSFS compiler and it is solved by changing tiling dimensions, or by projecting more directly onto a polygon in a "one to one" ratio.

 

[RicherSims]

Thank you @rhumbaflappy and @=rk= for the responses. I can confirm that the polygons where the issues occurred were indeed triangulated before export from Blender. But Rick seems to have identified the real issue.

Everything you've described is a consequence of allowing UV offsets to increase beyond the zero/one range. It is a known limitation of the MSFS compiler and it is solved by changing tiling dimensions, or by projecting more directly onto a polygon in a "one to one" ratio.

Thank you Rick.
I had written a script for my UDIM workflow in Blender and I forgot to move the UV's back to the 0-1 UV space for the final textures that were baked.
I was totally unaware that the MSFS compiler had issues with that.

 

[fabs79]

Does this mean that msfs doesn't display repeating / tiling textures correctly? That would be a major letdown because you'd need much higher resolution textures to achieve the same resolution if you can only use a non repeating texture sheet. For example I built a hangar with a large, rectangular window in the back where in reality the window consists of 8 identical elements, so I created a 1024 x 1024 texture for the window element and made it repeat 8 times on the u axis. To get the same quality I'd need a 8192x1024 with a non repeating texture or am I getting something wrong here?

 

[=rk=]

Tiled textures are also subject to the zero-one range rule and in my experience, are easier to keep within that range.

 

[GaryGB]

Hello:

You may wish to review the recent info regarding Sketchup Material auto-self-tiling versus discrete pixel vertex UVW mapping revisions with the Make Unique Texture and Combine Textures features ...posted here:

https://www.fsdeveloper.com/forum/threads/material-colors-not-displaying-in-msfs.453561/post-890748


Additional recent info pertinent to use of Sketchup Combine Textures feature is posted here:

https://www.fsdeveloper.com/forum/threads/i-use-model-converter-x.453693/post-891214

GaryGB