Option to choose and set glTF appearance/shading setting for Cesium 3d Tiles writer
For example, options to set metallic factors, roughness factors etc. Or option to choose if for example "KHR_materials_unlit" extension is used.
Materials unlit extension would improve appearance especially for buildings with image textures. Now buildings with image textures tend to get too dark because of the shading, and changing these settings manually is time consuming and difficult.
