Hello,
the new FBX importer introduced in 5.5 crashes the editor when importing a static mesh that has multiple materials → this happens if some polygons have unassigned materials.
Here I imported a Mesh with 4 Materials, but i have missed some polygons which had no materials. The moment you press import, the editor crashes. This is what the crash reporter spits out:
Assertion failed: (Index >=0) & (Index < ArrayNum) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 783]
Array index out of bounds: -1 into an array of size 4
Of course its not good if there is an unassigned material. A warning would be nice. If i remember correctly the old importer just made a new material…not sure. I would prefer a warning tbh. Took me quite a while to figure out what the cause of the crashes were. The array index out of bounds in the error report changes depending on the amount of material slots.
I am surprised this is news. I kind of like that is checking my assets, although in a very cruel manner. I create most assets in Cinema4D. I export stuff manually.
I give you a simplified FBX to test it. A cube with only one material, but one polygon left out with no material. It will crash. have tried on 3 machines on different projects. good luck
I also found a second way the importer is crashing:
When you have more than 1 material on your mesh, lets say 3 and for instance the second material does not have UV projection but something else like Spherical projection, then at the import stage it crashes. the be more exact, I think it crashes when it has to generate a uv set set for a material slot. the fbx file however is fine in itself and i can open it in other software.
Legacy importer did the following: it imported the materials in order, once it hit another projection method it then created a UV for that from that projection, but then skipped rest of the materials, and then you only ended up with 2 material slots instead of 3.
Here is an example
All Polys have a material assigned. 3 Materials, the second one is set to spherical mapping instead of UV. Again, it will crash. handle with care.
I also deactivated stuff like material search, most settings are basic, i just have force X Front axis. If you need the specifics I send you. But its not that, i’m sure
