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[Solved] 4.24.1 seems to crash importing very basic skeletal FBX (from Blender)

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    [Solved] 4.24.1 seems to crash importing very basic skeletal FBX (from Blender)

    [ UPDATE - FIX ]

    Ensure the FBX skeletal mesh has a Material (in Blender). Many thanks to
    Yaroslav for his answer below.

    [UPDATE - This is a bug. ]
    [ https://answers.unrealengine.com/que...1760/view.html ]


    I've never had any issue importing rigged meshes from Blender to Unreal before. In fact, it's always been a breeze.

    However, since I upgraded to the latest version, I'm getting a crash as soon as I click the import button to confirm import settings.

    For instance, I created a simple cylinder mesh with, say, 4 linked bones in it so it moves like a bendy-straw. I've reduced the complexity of objects again and again but it seems to be something in this latest version that causes this crash regardless of the mesh or how many bones or even how those bones are linked.

    To be sure, I re-installed an older version of Unreal (4.16.3) and all the files import fine!

    Here is the error I get with the recent version:
    Code:
    Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 614] Array index out of bounds: 0 from an array of size 0
    Last edited by Arkiruthis; 01-11-2020, 01:15 PM. Reason: Edited post to add fix details.

    #2
    Did you try deleting 4.24.1 and reinstalling clean? I've had strange update behaviours in the past with version updates.Clean installs usually fixes it.
    Clarke's third law: Any sufficiently advanced technology is indistinguishable from magic.
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    Comment


      #3
      Originally posted by FrankieV View Post
      Did you try deleting 4.24.1 and reinstalling clean? I've had strange update behaviours in the past with version updates.Clean installs usually fixes it.
      Hi Frankie, yeah it's definitely a bug as other people are now reporting the same thing (via the link I added to the original post).

      I did re-install again today just to be sure but the assertion error leads me to believe something has changed in the way the MeshBuilder is reading the data.

      I filled out the bug report, but when you click "submit" it doesn't take you to a confirmation page. I suspect they may receive about 8 of the same report from me...

      Comment


        #4
        Hello, I took a look at the the skeletal box in the link you provided from AsnwerHub. Yep, it crashed, it looked like a problem I encounter couple of weeks ago. Basically, regardless of whether you choose to create or not create material in Unreal's FBX Importer it will crash if you don't add material in Blender before exporting skeletal mesh. So if your model doesn't have a material, simply open your model in Blender, add a material, and export it. Then Unreal's importer shouldn't have the problem. If you have material added/applied to mesh already, but yet it still crashes, then, I'm afraid it some sort of other issue.

        Funny, as far as I remember, before Unreal could easily import model whether it is skeletal or static mesh without material, but now only static models can be imported w/o material applied beforehand. For skeletal meshes, you need to manually add them materials in blender.

        Comment


          #5
          Hi Yaroslav, that's it! Thank you!

          This all started when I wanted to test an alternative to using Unreal's Cloth simulation. So I created a plane, added some bones, exported and found that it was crashing.

          Looks like I forgot to add a default Material . So every test object I exported from then on, I forgot to add the Material.

          Would you mind copy and pasting your post as an answer on the Bug Report post I linked above? (that way you rightly get the credit for solving it )

          Comment


            #6
            Originally posted by Yaroslav Osipov View Post
            Hello, I took a look at the the skeletal box in the link you provided from AsnwerHub. Yep, it crashed, it looked like a problem I encounter couple of weeks ago. Basically, regardless of whether you choose to create or not create material in Unreal's FBX Importer it will crash if you don't add material in Blender before exporting skeletal mesh. So if your model doesn't have a material, simply open your model in Blender, add a material, and export it. Then Unreal's importer shouldn't have the problem. If you have material added/applied to mesh already, but yet it still crashes, then, I'm afraid it some sort of other issue.

            Funny, as far as I remember, before Unreal could easily import model whether it is skeletal or static mesh without material, but now only static models can be imported w/o material applied beforehand. For skeletal meshes, you need to manually add them materials in blender.

            Thank you so much! Was about to throw either myself or the computer out the window

            Comment


              #7
              it's 2020 and with blender 2.8 and unreal 4.24 this problem is still a thing.
              thankfully the same fix of adding material in blender is working too, so thank you so much!

              Comment


                #8
                How are you going to ever use a mesh in engine without a material? You won't.
                There is literally no reason to fix this. Every mesh NEEDS a material assigned for proper usage - and that's likely why it's still a thing in 2020.

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