Hi,
I have noticed that there is a difference in displaying .glb files between desktop and mobiles e.g. on Facebook. The files exported from babylonjs.serializers using GLTF2Export.GLBAsync() or 3DS max + Babylon JS plugin has strange reflection despite of specular=0, roughness=1, metallic=0 etc. I have tried many combination with Std and PBR materials and I always have this strange reflection on mobiles.
I decided to try Modo and the effect is much better. So probably you have a bug in babylonjs.serializers and 3DS max plugin. I have noticed that in attached file called "babylonJS.glb" which was exported from 3DS max "roughnessFactor" is 0.9 and should be 1.0 if I use standard material with specular = 0.
GLB files:
Modo.glb
Screenshot from the smartphone (Android/iOS, the effect is the same), 3DS max + Babylon JS plugin and the same effect after using babylonjs.serializers.js GLTF2Export.GLBAsync() method:
Screenshot from the smartphone when Modo was used (on smartphone the box is totally black - so the effect is actually perfect).
And the effect which we can see on the desktop web browser (as you can see the file exported from Babylon JS is not totally black, but it should be. However the worst thing is this reflection on mobiles):
