[gltf] Use alphaMode for common materials as well as PBR.

examples/js/loaders/GLTF2Loader.js

@@ -1958,14 +1958,6 @@ THREE.GLTF2Loader = ( function () {
 
 						materialParams.map = dependencies.textures[ metallicRoughness.baseColorTexture.index ];
 
-						var alphaMode = metallicRoughness.baseColorTexture.alphaMode || ALPHA_MODES.OPAQUE;
-
-						if ( alphaMode !== ALPHA_MODES.OPAQUE ) {
-
-							materialParams.transparent = true;
-
-						}
-
 					}
 
 					materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
@@ -1991,7 +1983,9 @@ THREE.GLTF2Loader = ( function () {
 
 				}
 
-				if ( materialParams.opacity !== undefined && materialParams.opacity < 1.0 ) {
+				var alphaMode = material.alphaMode || ALPHA_MODES.OPAQUE;
+
+				if ( alphaMode !== ALPHA_MODES.OPAQUE ) {
 
 					materialParams.transparent = true;