Can't work with datasmith


I’m having a situation here for a long time and i really tried all kinds of solutions i found online.

These problems repeat in both 4.26 and 4.27 versions of Unreal.

I’m working with 3d max 2022 (previously 2020) and no matter what i do, my geometry always have problems when imported into Unreal. Degenerate triangles, lightmap errors, flipped faces, you name it.

I tried generating lightmaps automatically, also tried using unwrap inside 3d max, exported as fbx, .udatasmith and there seems to be no way to make it work it out like it should.

I tried modeling just a few simple geometries and send it to unreal and it still show some kind of problem.

s there a specific workflow that i’m missing? Can anyone here show me the light?

Thank u all!

Degenerate geometry and overlapping lightmap UV warning messages can usually be ignored.

Do you have (visual) examples of exported scenes with issues ?


Sorry, right now i have nothing.

But as soon as i can i’ll take a fez SS to illustrate.

Thanks Antoine.

Hi Antoine, how r u doing?

Well, now i’ve got the time to maek one more test and it really shows what i was saying.

Here is the scene i am trying to work on, all set after importing the datasmith (Direct light, sky atmosphere and Sky Light) then after build all black. Then i created some spotlights indoors, but got the same result after the build, as you can see below:

Then i sent it to a friend who works very well with UE and for a very long time, for him to check for any possible mistake i missed. After the download he just opened and started the build, no config changed, nothing, the same file even with the same viewing position…

Me and him are both using Luoshang GPU Lightmass, but i don’t understand why this is happening only in my machine, since the settings are exactly the same…

I’d appreciate any help in this matter, it’s driving me crazy…


This is more of a question for the GPULightmass thread then, however the meshes are imported (FBX or Datasmith), once the geometry is in engine it should behave the same.

Have you tried native GPU Lightmass ? You mentioned Luoshuang’s, so are you talking about the old GPULM plugin ?


For this specific project i used datasmith, but either DS or FBX show the same symptoms.

About the GPULightmass, despite being Loushang’s or the native, what bugs me is the fact that in the other PC it worked like a charm, with the exact same settings and everything, i mean, it it supposed to work the same way in all equipments right?

And the plugin is not THAT old, since there is a version for the last unreal 4… -.-

Thanks again for the feedback!