Blender File with Sub-division .fbx file import into Unreal crashes

Development Asset Creation
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Hi,

I have several models in Blender I wish to export to Unreal.
Some models that don’t have the modifier “Sub-division Surface” export into the Unreal engine fine, but the models that do have sub-division surface makes Unreal freeze at 75%.

I recently un-installed Unreal Engine and re-installed it so it’s at v4.10 and I cannot figure out the problem of why Unreal is crashing when trying to import models from Blender with sub-division applied.

2

Three quick questions:

  1. Are you applying the modifiers through the fbx exporter (Apply modifiers is checked)?
  2. How heavily subdivided are the objects?
  3. Which version of Blender are you using, and which version of the fbx exporter (binary or ascii)?
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  1. I am applying the modifiers in Blender, and then I have got the "Apply Modifiers, Smoothing set to “Normals” " checked when I am exporting to fbx.
  2. The subdivisions are set to 4. All of them.
    I first created objects, subdivided them and then joined them together.
  3. The version is FBX 7.4 binary
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Alright, my first thought is that Unreal isn’t actually crashing, but the file is large enough that importing it is taking a long time, causing the engine to appear frozen. If the final object has a particularly large number of vertices after the subdivisions this might be the case, and it would explain why the un-subdivided object imports without issue.

A quick way to test this: try applying only 1 level of subdivision instead of 4 to the original un-subdivided object, and then see if the resulting object will import into unreal (it should take longer than the original, but not nearly as long as the one which was more heavily subdivided).

Hopefully that is the only issue, if not we’ll get it figured out!
-Noah

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I tried what you said and it worked! I applied 1 level of subdivision and left it for 10 minutes and the file successfully imported.

I thought that Unreal had crashed because in Windows Task Manager, it said “Not Responding” thus I closed it.

Thank you so much for your help!

I have another problem though: When I import my fbx file, it says my object “has degenerate tangent bases” however when I look at my object in the game world, nothing seems to be out of place. Could you explain what it is and if it’s possible to fix?

Kind regards,
Yuushi

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Thank you for your help!

I will try it out and get back to you if I have any more problems ^ ^

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Woo hoo, glad it was that simple!

The degenerate tangents are due to issues with a UV channel, this question has some good explanations: Degenerate tangents question. Basically, you need to create and/ or fix up the UV map for the object.

Cheers!
-Noah

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Yeah you gotta be careful with that subsurf modifier. I generally model with it and then turn the eyeball off to disable it tonsee how the model looks and what needs adjusting then I delete it and smooth the faces. The subsurf modifier was before the multi res modifier came out for sculpting and was supposed to be used for high poly baking to low poly meshes. In some circumstances you can keep it on but its really only good as a guide as there may be some parts of the model that don’t need that many triangles and take up your memory budget.
As for the degenerate bases. Make sure you don’t have overlapping vertices or that the uv shells didn’t get moved outside the texture space.
Cheers

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Thank you, I will keep that in mind