order of materials changes on reimport
Update: this problem is still present in UE 4.15.0-3258144, brand new project, with only one Static mesh imported. At the moment only viable solution is to work on the assests in version 4.13 and when model gets finished/approved then export it to 4.14/4.15p
----- rest of the report is for 4.14 -----
In my 3ds max asset creation workflow I use 1 dummy box as a master parent with all the geometry meshes and UCX pieces linked to it. This helps to maintain pivot of the asset even after serious changes of the asset's dimension and so on. Since upgrading to 4.14 i am frequently running into serious issue.
Depending on what meshes linked to the master parent and what IDs those meshes have material ID swaps after reimport.
Let's say i have asset made from multiple meshes and i import it into UE. I assing materials to the IDs and all is fine. However, if merge some geometry in 3ds max and then reimport, materials get randomly swapped.
To illustrate my point i made few screenshots:
If i export left (merged together) one, asset in UE looks as it should, all materials are in correct places.
If i export right one where multiple meshes are linked to export node, asset in UE looks differently. Notice how materials slots in the editor stay same but slots in the asset LOD0 section changes for no apparent reasons. (bottom right corner of the image.)
Another example could be changing small detail on asset and reimporting it again. It leads in to another random change.
Steps to reproduce.
Info that may be relevant.
I've posted this question on the forum hoping it was simple problem but no one could provide answer so i am looking for solution here. Link to thread
I cannot find mention about this problem on the internet so it's possible I am doing something wrong. Help please. Thank you, H.
We actually found a new import issue regarding material ID assignment. This has to do with FBX files with multiple meshes. If you select "Combine Meshes" upon import the bug will occur. The only know workarounds are what you have already stated. By combining the mesh prior to import.
You can find the issue here: https://issues.unrealengine.com/issue/UE-40814
Keep in mind we may not prioritize or address the issue quickly. We do gauge community interest through votes so if you feel this is important spread the word and vote!
answered Jan 18 '17 at 09:06 PM
For anyone still interested in this. Unreal will assign material slots in a ranking order that mimics the meshes ranking order in your 3D modelling program.
Example: if I have a mesh containing 2 cubes crashed together. My outliner in Maya may look like this:
Thus whichever material is assigned to Cube_01 will appear in Material slot 1
If the order of these changes during edits and the outliner looks like this:
if I reimport from this state then it will appear as if the materials have swapped position in Unreal
So just be aware of how things are ordered in your scene before export, as this will directly affect material slot ranking on import.
If you have a single mesh with multiple materials on in and wish to change material slot order. The easiest way I have found if to just break the mesh apart and make sure the corresponding faces are in the order you want.
answered Mar 21 '19 at 04:43 AM
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