Hello, to save space we’ve been putting AO, Metallic and Roughness on the same texture, but a friend of mine told me that he read that it should be on separate files. Is that true? If so, what are the differences? Thank you.
It shouldn’t be a problem as long as you get the results you desire. By using less texture samples you save memory. On the other hand, you might get better results by putting ambient oclussion in another texture, since its generaly smother than roughness and metallic.
If you are concerned about memory usage, it is a common practice to have a high ress base color map and normal map and lower res metallic, roughness and ao maps. e.g. you could use 20482048 for your diffuse or base color and normal maps and 512512 for the rest of the samples.
But, in the end, it only matters that you get the result that fits your needs visually. What you are doing has no downsides in terms of performance.