The format does expect the textures in a specific format, however. The Base Color, Normal, and Emission textures are saved as individual files, preferably a PNG as the format is lossless. The Ambient Occlusion, Roughness, and Metallictextures are saved in a single channel-packed texture to reduce the number of texture loads. The textures need to be packed into the channels of your texture as follows:- Red: Ambient Occlusion
- Green: Roughness
- Blue: Metallic
Going forward, I will refer to this channel-packed texture as the ORM texture for Occlusion, Roughness, and Metallic.
So Orange is what you see when all 3 Layers are overlayed ... here Red over Green :-)