I'm working on some game textures, and the alpha channel controls Metallic or Roughness, instead of Transparency. I mapped them accordingly onto the principled BSDF (e.g. RGB channel goes to base color and alpha goes to metallic) and it did work well in Eevee, but when i changed to Cycles, the colors are washed out and it only renders alpha channel. Guess this is due to Cycles wrongly taking the alpha channel as transparency (by default?) so my colors are missing.
I've tried several ways but nothing works:
I duplicate the texture input node (and make it single-user) and, get RGB channel from one node (alpha channel disabled) and get alpha channel from the other node (alpha channel set to be straight under N panel - property). Two steps work well separately - i got colors when i link RGB node to base color, or i got metallic mapped when i link the alpha channel node, but when i linked both of them onto the BSDF, colors are washed out again.
I make a copy of the original texture image, get RGB channel only from img 1 node and alpha from img 2 node. Same result as 1.
I edit the original texture image in photoshop. Now image 1 only contains RGB channel (provides only RGB) and image 2 contains both RGB & Alpha (provides only alpha channel). not working either.
I try to do an image 1 with only RGB and img 2 with only alpha in dds format, but got a error msg in blender saying the dds file is not readable and my model turns to purple / pink with no textures.
I'm feeling that although i link only alpha channel from node 1 to BSDF - metallic, blender somehow still reads the RGB channel from node 1 and overwrites my RGB channel from node 2.
Any chance you can render ONLY the alpha channel and let blender ignore its RGB channel? Or any chance you can apply the base color (in RGB channel) and the metallic map (in Alpha channel) simultaneously onto BSDF in Cycles, just like in Eevee?
This is pretty weird, I've dealt with several texture images with Alpha channel controlling transparency and the problem never happened before. First time working on game textures with alpha controlling metallic or something.
Thank you in advance!