GLTF Viewer shows mesh almost black on complex meshes

[Peter_Dragonstone]

Good afternoon,
very strange thing is going on with complex meshes (that cut with boolean modificator).

same exact material, no difference but it shows in a very different way (almost black). I checked normals, they look the same.

in the same time, polygons that “modeled” work fine

tried to figure out but nothing works.

here’s fbx and glb
3.glb (10.6 KB) 3.fbx (21.3 KB)

[mjurczyk]

After importing your glb file to Blender it shows 2 different materials on models:

1. Default white material:
   

   

2. Black material, in which color is multiplied by vertex color which is 0, resulting in black: