thanks for the super fast reply; but… can you edit any other format directly in photoshop or in gimp? Or is it just an option for psd?
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You can edit every texture in gimp or photoshop, but you wont be able to keep all the layers/effects/… e.g with psd I can have different layers in my file -> then I can save and import it into the UE4 -> after some time, when I have to edit something in the texture, I can just open the psd file and then I can still edit stuff in the file (e.g delete a layer,…)