Why does FBX import take so long for a large high poly mesh?

Is it possible to get some Alembic love in this house? FBX is such an outdated POS. Takes me 24 hours to import a 700 meg fbx file with LOD. Pulling up an error message for tangents causes the process to take even longer. Because you have to hit the OK button after each piece of geometry. Please save that for the end of the process after it imports. For a detailed report instead of stopping after every error. It’s automotive CAD data. It will always be jacked up.

Also, the time reporting in the Log for import of each piece seems to be incorrect. I am getting 15 minutes for one piece of geometry that I can bet is taking a lot longer than what UE4 log is displaying.

Would be great to support hierarchy grouping as well on the import for static geometry as well.

I love UE4 but hate the way FBX is handled in it.


I was able to comment this line out of the source code and save a ton of time. It really puts the FBX import process on cruise control.

From: Runtime/Engine/Private/StaticMeshBuild.cpp

// FMessageDialog::Open(EAppMsgType::Ok, WarningMsg);

I am not a programmer but to do this wiith the source code is a huge deal. My import time is now 2.5 hours. Geometry looks great aside from the errors it was reporting.

Hi Metzger,

From the sounds of it, it seems like you’ve got a very complex mesh to be that large in size. I’ve got a test mesh asset that is 1 million polys and it’s only clocking in at 159mb. That file can take 5-10 minutes to import with our machines.

What is the poly count on your mesh?

While there is no limitation based on the number of polys your mesh can have, but there are limitations on how much your system can process.

What are you system specs? You can post your DxDiag here and it all cover all the information. You can get your DxDiag by going to Start > Run > DxDiag and then save all information. This will output a text file.

Thank you!


Hi Tim. I am at around 5 million polygons including LOD of 3 levels. Here is the DXDiag: http://pastebin.com/Sk5NzDhX


While the engine can support any mesh size I’m not sure this is the best approach. 5 million polys for a single mesh is a lot for a real-time engine. Your specs seems good enough but even still with our machines running GTX-770s and 32gb of Ram a mesh this large can take a while to import.

Are you LODs included in the 5 million polys you’ve mentioned or on top of the 5 million?

Are you able to reduce the poly count and bake a normal map on your mesh?

I also want to mention that my vertex count inside of UE4 is 6 times the size than what I am getting inside of Maya. I wasn’t sure if this is normal or not. The cad Data is already triangles. I also have only 1 UV space.

Hi Tim. Yes, With all LOD its around 5 million in total. Frame rate isn’t an issue. I just strip out everything I don’t need. Like lights. Unfortunately baking normal maps isn’t an option for the current workflow. Displaying the polygons isn’t an issue to be honest.

It’s just very painful to bringing FBX into the engine. Is there anything that can be multi threaded for FBX import? Like each piece of geometry to get its own thread on import? It only pegs 1 core and is not using much ram while importing.

With large meshes you’re going to see this large import time when it’s processing the data for use in UE4.

To test import length I made a sphere with 15 million polys that was around 600 mb and imported that single mesh into the engine, but it took over an hour with my machine. This may vary from machine to machine dependent upon specs.

While the engine does run smoothly with the object in my scene it will take a while to import. This is not a problem with FBX import so much as it’s a large file that has a lot of information to process.

Thanks Tim. To be honest the error messages popping up were causing it to be a very unproductive import because it would hold importing the next geometry pieces until you hit ok on the error dialogue. Thank you for looking into it though. I don’t mind the wait as long as I don’t have to babysit the application while it imports. :slight_smile:

Wow. Any size? What about Z sorting? Afaik poly sorting making huge impact on fps.

Is there any improvement on this? FBX import times are still insane for hipoly meshes. It’s very very counterproductive.

ive tried to import a 100 mb face scan… so far its been going for about 16 hours… Funny fact… if i import it as an obj it imports fine… Why does the fbx importer suck?