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Alpha channel pass

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  • Alpha channel pass

    I would like to request the alpha channel that can be created by checking the "process alpha" option, as a pass under the Render Elements. Right now it's not possible to save the alpha as a separate file, only incorporated in a PNG file.



  • #2
    Why do you need alpha as a separate channel? It is not easy to render alpha without rendering the whole image.


    • #3
      Hey Andrey, I think he means like an alpha pass in the render elements.


      • #4
        I understand what he means. I am thinking about what it is usefull for.


        • #5
          Yes I know, I'm talking about being able to save the alpha channel when you are rendering a whole image. There are probably a lot of reasons for an artist to have a separate alpha pass instead of losing the background of the render. As of now I have to choose between rendering an image with the alpha included, so no background, or a full beauty pass with the background but without the alpha channel. So usually a Multimatt functioning as a mask will suffice but if you are rendering something that has glass then a mask won't work. But I'm sure there are a lot more reasons to have a separate alpha channel which I can't think of right now. It's just nice to have for compositing.

          So I don't think it's necessary to have the alpha channel render separately or faster than the beauty pass, just let it go along the beauty pass. I think it would be nice or even normal to have the alpha channel as a separate pass. It's a luxury that Fstorm renders out all passes instantly. With corona for example you have to wait a bit before even a mask is complete. So it's normal that rendering out an alpha channel takes a while.


          • #6
            The whole idea of alpha is to replace background income with alpha and then use some different image in post processing. But I can adopt some fstorm render element for using as alpha.


            • #7
              I know, but when compositing in AE or something similar it's always nice to have this as a separate option. Sometimes I just included it for the sake of having the ability to use it later on. In my personal workflow it is nice to be able to keep de background and also get the object separated by an alpha (or mask for opaque objects) so I can edit them separately.

              Would be great if you can adopt a render element for this, thanks.

              On another note, atm when rendering the alpha channel and viewing it in the RT window, it does not get updated. It only gets updated when switching between the beauty pass and alpha pass. FYI, just a small note.