I have problems importing some meshes. Some faces of the mesh are missing (inverted?). It seems only to happen with meshes that were constructed with some booleans involved. I had converted them back into editable polys before UV mapping them. Other meshes that are just simple boxes or have just some bevels/insets import fine. Also in one case it worked for a door.
I have added a zip file containing the following:
–The FBX file(s) that I used. “InnerWallWindow” is the troubling one. (while Inner WallDoor looks just fine).
–The max scene file from which the fbx files were exported.
–The textures that were used (for completeness)
–The UASSET files that were cerated by the engine on import.
–A couple of screenshots illustrating the problem.
I took a moment and looked into your issue here. I was not able to see any faces that were flipped necessarily with my test and even flipping the faces that were inverted didn’t seem to help in UE4. I’ve not seen that before.
Although, going through and cleaning up the geometry a bit I was able to get it to no have the inverted back face.
It’s best practice to not export any geometry that has Ngons. This seemed to be the problem. In the image you will see that I’ve cut edges into the corners to either triangulate or make a quad. The engine will triangulate a mesh when it’s imported, but there can be side effects such as the inverted back face. In most instances though the engine does a really great job at working with Ngons though.
The reimport worked flawlessly, updating the UV sets. Very nice indeed.
I guess I should pay a little more attention to the mesh topology. if it looks ok in max doesnt mean its suitable for UE4. Lesson learned.
A nasty thing that Max does if you use the mirror tool, for example, is it will flip faces that does not get updated as part of the visible viewport. Another nasty thing is Max adopts the local transform of an object being attached. This usually results in unusual behavior like strange lighting effects or in your case flipped normals even though everything looks just fine in the viewport.
A habit to get into is to use the xform reset found under the utilities tab which will reset the object to it’s true state and set the local transform to the relative world scale.
As for Ngons you bet UE4 handles them just fine as I do have a habit of using Booleans a lot.
Maya does that too. Usually, if you freeze the model, these flipped Uvs will return to normal. If not, you can still reverse normals manually. You shouldn’t use Boleans, if you can avoid it and no engine handles Ngons well. Every DirectX Engine deals with triangles (hence "triangulation), If you have Ngons in your model that can’t be triangulated, you get shading errors or worse. There are a few simple rules to obey when working with realtime engines and the most important one is ALWAYS USE QUADS
Thanks for the kind words! We’ve got a small but dedicated team who is glad to engage with the UE4 community and offer help where possible. Although we don’t have the resources to respond to every discussion, we certainly do as much as we can.
I experimented a bit and its eems that NGons are no problem unless they have “holes” in them. Hence my Door mesh worked, just two U shaped Ngons there.
So Im surprised that qour windows work…
