@UE_FlavienP you are right.
Time has passed and I continue to test MaterialX in Unreal.
One thing I could never figure out was the triplanarprojection approach, especially with normal maps (vector3).
I took the test file from @Gladiator_FX95 and added some more geometries and materials (mtlx files). If you load “test_stage.usda” with Unreal (I tested with version 5.4.2 with Substrate enabled) you can see the failed attempt to apply the flake texture using triplanar mapping.
usd_mtx.zip (5.0 MB)
Has anyone successfully used triplanar projection?
If you want to have a look at the shader graph, I recommend to download Quiltix (https://prism-pipeline.com/quiltix/).