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I have used Blender layout and modeling tools to create, shape and size a number of meshes with fairly-simple shapes. Most of them when outputted to FBX, OBJ and X3D files appear in viewers as they do in Blender. A small number of my objects when output and viewed in an FBX or OBJ viewer display with "wings" that do not appear when these same objects are viewed in Blender.

The first image here shows what each of two cube meshes look like in Blender with Viewport Shading and X-Ray settings in place:

Viewport Shading and X-Ray views

The second object, not shown here, appears the same when it is selected. Neither object has superfluous vertices.

When the two objects are output to FBX and viewed in the 3D Viewer built into Windows 10, one of the objects (the same one shown in Blender in the photo above) displays with "wings" which form triangular faces connecting vertices which do not have connecting edges in Blender. The other object displays in the 3D Viewer as I would expect, without added faces.

FBX output from Blender, two meshes which appear differently which should appear same but for size

Here is another view of the misshapen object, offering a clearer glance at the plane-like angles that get affixed to the 3D object.

FBX output from Blender limited to the misshapen object, showing view that emphasizes unwanted wing-shaped extraneous content

I have made numerous attempts to fix the problem, such as by doing workarounds. I have tried deleting all of the faces and then putting them back in. I have tried replacing the faces by highlighting just two or three edges at a time and adding back the faces triangle-by-triangle, and then dissolving the face segments into a single face per side once all the pieces were in position. Nothing I have tried has worked.

I have used no modifiers in creating or adjusting the shapes. I used nothing for the materials but solid colors chosen in the Base Color and Viewport Settings boxes. A perplexing aspect of this problem is that I don't know of any steps that I performed differently in creating the objects that displayed as intended as against how I created the objects which display with undesired add-ons.

Seeking information, I exported the two shapes separately from Blender to OBJ files, and then looked at the code in a text viewer. Although the two objects are the same except for measurements, the number of code lines is different for the two objects, with one seemingly having more twists or angles than the other.

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This is the result of using ngons. If you add the following edges so that the faces are all quads (on both top and bottom), this should resolve the issue;

enter image description here

As you'd mentioned before, technically all Tris would work too. The issue is that you're dissolving the faces into a face of (what is generally considered) irregular dimensions/vertices. This doesn't cause a problem in Blender because it inherently supports ngons (faces with more than 4 edges/vertices)

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  • $\begingroup$ This didn't resolve the issue. I went back to an earlier version of the object which had the vertices at the points where the two red lines were drawn onto the photo (I didn't delete those vertices until a later revision), deleted the top and bottom faces, created three quad faces on the top (as shown in the markings), another three quads on the bottom, then dissolved each group of three faces into one face. All sides looked fine when viewed in Blender, but the wings showed up again when viewing the FBX. $\endgroup$
    – DH_in_USA
    Apr 2, 2020 at 21:45
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    $\begingroup$ Stop dissolving the faces. That's the direct cause of the issue. $\endgroup$
    – AlexanderESmith
    Apr 2, 2020 at 22:15
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    $\begingroup$ The suggestion immediately above worked. By leaving faces separated rather than merging all faces on a given side using the "Dissolve Faces" command, I successfully outputted FBX and OBJ objects shaped as seen in Blender. The six objects that I made that exported with misshapen extraneous features were fixed, and now they have joined the forty or so objects that I made using the same methods which never output with extraneous wings. I remain perplexed as to why the difference (I used Dissolve Faces on the forty), but I accept that as an odd behavior as found in many computer programs. $\endgroup$
    – DH_in_USA
    Apr 3, 2020 at 20:38
  • $\begingroup$ Wonderful :D Please mark the answer as the Accepted Answer for future users. $\endgroup$
    – AlexanderESmith
    Apr 3, 2020 at 21:31

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