Import FBX chunks creates material IDs

I have a simple FBX with 10 elements/objects that all have the same material when I use that as my destruction chunks with import FBX chunks UE4 generates 9 additional material IDs, 1 for each element even though those IDs don’t exist anywhere in 3DsMax.
Is it then also 10 draw calls?

Hi Davison,

This isn’t a bug, but simply something that has not been written in yet. It’s on the bucket list of things to do, but currently is backlogged. The addition of this feature has been entered with UE-8566.



Thanks, looking forward to it. Can you also look into this problem I have with destruction: Fracturing with 2 depths and modeled chunks? - World Creation - Unreal Engine Forums

No problem. I’ve assigned myself to the issue, but it’ll probably be next week before I can try and set something up.

Hi Tim,

I noticed that this hasn’t been implemented yet and so submitted a fix for this. I also noticed that unique material IDs were assigned per section, increasing the draw call count on imported FBX chunks (doesn’t affect Voronoi fracture).

Here’s the pull request.

Hopefully it at least helps someone out there :slight_smile:


Has this been fixed in a new version? Still does it in 4.15.
A material slot for every chunk is kinda crazy. 500 chunks and you have to manage 500 slots. If that are really 500 draw calls it is pretty much unuseable.

It’s not released mainline yet, but the fix I submitted was pushed into master about 16 days ago :slight_smile:
I assume that the fix will be included in 4.19 - but don’t quote me on that, I’m not Epic staff.

You can keep track of it here.

Great! Hopefully it will be in 4.19.