@sebavan
Okay I found the problem it was something about the backfaceCulling …
To see what I’m talking about, go to this link and change line 208 to true.
https://playground.babylonjs.com/#84PA1Y
(The material apperently hide the sprite if backfaceculling is set to true)
So as @Deltakosh said in GLTF Model (from 3DS exporter) does not generate shadows, faces may be flipped when importing a glb there’s something about right handed and left handed.
The guy who created this topic had to set the backfaceCulling to false to see the faces correctly.
Is there a way to avoid to set backFaceCulling to false or avoid this kind of inversion ? Because let backfaceCulling to true can reduce perfomances ?