How to use alpha-map with glTFLoader.js?

I hope to get the transparent hair in a glTF model with alpha-map,but it does not work well.
I do not know how to resolve this problem.

Try to iterate through the materials like so and configure Material.alphaTest like so:

gltf.scene.traverse( ( object ) => {

    if ( object.material.alphaMap ) object.material.alphaTest = 0.5;

} );

I configued Material.alphaTest in the glTF model file with blowing code.