Make sure `on` flag for specularGlossiness is being persisted

code/glTF2Exporter.cpp

@@ -426,6 +426,7 @@ void glTF2Exporter::ExportMaterials()
                 KHR_materials_pbrSpecularGlossiness = true;
             }
 
+            m->pbrSpecularGlossiness.on = true;
             GetMatColor(mat, m->pbrSpecularGlossiness.diffuseFactor, "$clr.diffuse", 0, 1);
             GetMatColor(mat, m->pbrSpecularGlossiness.specularFactor, "$clr.specular", 0, 1);
             mat->Get("$mat.gltf.glossinessFactor", 0, 0, m->pbrSpecularGlossiness.glossinessFactor);