The PhotorealisticScene sample is the example that shows our Photorealistic Render plugin in action. It has two configurations. When you start the sample you can choose two configurations: gltf or ogre_mesh. The ogre_mesh option is going to show you a scene with PBS materials loaded from a .mesh file.
ogre_mesh configuration
The gltf option shows two glTF objects in the scene.
gltf configuration
The sample is using the apePhotorealisticScenePlugin to create light and to load objects from .mesh files as seen on the first picture. On the other hand, when you are using glTF, the models are loaded with the apeAssimpAssetLoaderPlugin. Be aware that if you are using apeAssimpAssetLoaderPlugin in your own sample you should not call ape::Event::Type::GEOMETRY_FILE_FILENAME in your plugin with a .mesh file because that results in crash.