I wrote down these steps. I'm a newbie and I think this is right
Correct me if I'm missing something.
How to create PBR Comp file in Photoshop for Blender
- if you have your AO, Roughness, Metalness each in a layer in photoshop......
- save each image into separate .psd files ( AO, Roughness, Metalness)
one at a time, select image and make it the only layer visible, then -> file->scripts->export layers to file
make sure "visible layers only" is checked, name and save (if you don't make sure "visible layers only" is checked, it will output
all your layers and if you have a lot, it will be a mess!
- you should have 3 .psd files for AO, Roughness, Metalness
- open all 3 files in photoshop as separate images
- change all to grayscale image->mode->grayscale
- also flatten the 3 images if not already (important) Layer->Flatten Image
- click on channels to view channels
- in the dropdown select merge channels (should be to the right of
the channels menu (four lines)
- run through the process and select the AO for the first channel, then Roughness and
- Finally change to RGB image->mode->rgb color
- save as a .png file with the name "name_COMP.png" with name being whatever you want to