Blender Exported GLTF rendered some materials partly black in scene

Question

Lighting: (The 2nd picture is using ambient light at 0.8 intesity. )

I tried ambient, Directional and Evironment lights, but no result.

Here is the Armature with all the materials in blender:

Here is how the model renders using GLTFjsx or GLTFLoader:

Answer 1

Thanks to @DonMcCurdy.

Solution

I had to convert my charcter's material type from spec/gloss to metal/rough.

Convert from spec/gloss to metal/rough before editing in Blender, requires Node.js:

npm install --global @gltf-transform/cli
gltf-transform metalRough yourModel.glb yourModel.glb