Channel Packing textures RMA on the channels of the RGB for the engine. SAVE format only TGA
Channel packing means using different grayscale images in each of a texture's image channels... Red, Green, Blue, and optionally Alpha. SAVE format only TGA
These channels are usually used to represent traditional RGB color data, plus Alpha transparency. However each channel is really just a grayscale image, so different types of image data can be stored in them.
Individual channels can be extracted by a shader to use them for particular effects, for example the red channel for glow, green channel for specular, blue channel for sound types, alpha channel for physics info, etc. Each channel can have a totally different layout, and thus use different UVs.
Games use this technique to avoid loading separate grayscale images, which saves Memory. However this does increase shader complexity, which can increase draw calls.
RMA is a type of packed map which contains Roughness + Metallic + Ambient occlusion, which are used with PBR (Physically Based Rendering).
