Exporting a large FBX map has parts with weird sizes

Heya, I have a large map inside of Blender, around 400 objects that I am uploading to Roblox as an FBX, however, some parts have completely different sizes as well as no collisions if I resize them. I tested it with the first 10 objects, this is what it looks like in Studio

This is what it looks like in Blender,

I have applied Rotation & Scale to all objects with Ctrl+A as well as setting the origin of all objects to 3D cursor, I cannot simply resize them as they have perfect resings, and like I mentioned the collision seems to disappear if I do resize them. It almost acts like a special mesh where the collision is small, near the middle of the texture, but the actual mesh texture is much larger.

I would really appreciate any sollutions.

Models which are flat do this when imported to Roblox. Try adding faces to the sides and back to prevent this.


This is just an example, it does not need to be as thick as shown in the picture. Hope this helps!

Is there a solution to this with flat objects? The entire map as well as all my other maps is flat.

Another solution is to rotate them slightly in blender before exporting them.

What exactly does that change? So I can just rotate it by 45 degrees and it would be the same size and position in Roblox studio where I can rotate it back?

I’m not exactly sure why this fixes it, but rotating them even the smallest amount fixes this issue in my experience.

Roblox does not support parts with a 0 size on any axis. Rotating the whole map 1 degree about the x axis for example would the the easiest solution (since parts are imported axis-aligned, rotating them this way will introduce volume), but the correct solution is to make sure any perfectly flat parts have a nonzero volume. Further, physics will behave more correctly with manifold shapes (no geometry holes, not a flat plane), especially those set to use hull collision, which is a bit against typical content authoring processes, but it is what it is.


Does rotating the map fix the collision issue if I rotate it back in studio?

Also can I get more information on the nonzero volume for the flat parts please?

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I did this, and it imported almost everything perfectly, however now just only some flat parts are completely invisible,

This has happened a few times, for the last time I uploaded it, this is the only part I found which is invisible. However, the texture may be the issue as I got a ton of errors while uploading.

V = l*w*h, if any of the components are zero, that’s zero volume. Just another way to say “don’t have zero size on any axis”.

When you import the parts into Roblox, because Roblox assumes the x y z axes are perfectly horizontal or vertical when determining part bounding boxes, any parts in your map that are perfectly flat planes will have a zero size on one of their axes. If you tilt the whole map, these parts are instead tilted slightly, so their axis aligned bounding boxes will always have nonzero x y z sizes (imagine a 2D box drawn around a slanted line versus a flat line).

This will fail if you rotate e.g. a 1 degree sloped flat face by -1 degrees such that the angle cancels and its flat in your authoring software again, but it’s very unlikely you have any exclusively 1 degree planes.

In studio you’d then undo the same tilt you did in your authoring software. You could possibly automate fixing the pivots too so they play nicely with the draggers. Remember though that this is a hack, and is just a shortcut to a working solution, rather than hand-correcting your 400 meshes.

These may be inverted, check double-sided in properties to verify, and flip the faces in your authoring software if so.

Otherwise you may be rate limited on importing, you can try breaking the import up into two batches if possible.

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