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  • Saving the alpha channel

    Hi,

    I feel this is a very basic question but I can't seem to find how this can be done. I want to save the alpha channel image as a separate file, how can I do this? I currently have a Multi-matte setup but that does not take transparent objects into account (because it's a mask which makes total sense). So how can I save the alpha channel Fstorm makes when checking the "process alpha" option, as a separate file?

    -Joep

  • #2
    Oke so I'm not trying to render out a PNG with the alpha channel baked in but Production Render does not show the alpha, just a black background. I wanted to steal the alpha channel from the PNG in after effects. I need to save the alpha channel somehow but atm I'm not able to. Why is there not an Alpha option in the Render Elements? Makes a lot of sense to me to have it there.

    I'm rendering an animation btw.

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    • #3
      There's no alpha pass, but a work around is to use the "FstormTexture pass and to put an "FstormColor" in the texture slot and set it to white. That will apply a white matt to all objects. I hope this makes sense, if not let me know.

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      • #4
        Last note is that it will still respect transparent objects.

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        • #5
          Hi
          You just have to check "Process Alpha" into the Kernel settings, start rendering, and in the RT window, to the left of save image icon select "alpha element" from the listbox. Now just save image.
          Software: FStormRender: 1.5.0h | Drivers NV: 456.71 | 3dsMax: 2020.3 | Windows: 10 x64
          Hardware: Gpu: GTX1080 Phoenix GLH | Cpu: i7-2600k@4.5GHz | Ram: 16GB | SSD: Samsung 860 Pro

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          • #6
            I think he wants it as a pass though

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            • #7
              Originally posted by arcfx View Post
              There's no alpha pass, but a work around is to use the "FstormTexture pass and to put an "FstormColor" in the texture slot and set it to white. That will apply a white matt to all objects. I hope this makes sense, if not let me know.
              Unfortunately that still doesn't give me the transparency of the glass that I'm rendering. I can make a mask with Multimatte that's not the issue.

              Yea I need a pass because it's an animation.

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              • #8
                I also tried using the refractions pass but I can't get the effect to be the same.

                I do think it's really weird that Fstorm has this feature build in, it can produce the correct alpha, but it's just not available as a pass...

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                • #9
                  Does Sylk answer the question? The only other way I know is to render the refraction pass out with alpha checked on when rendering.

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                  • #10
                    With "process alpha" checked, production rendering integrate alpha channel to the image files. If you save files as format which supports alpha it's ok, no? Doesn't what you need for the animation?
                    Last edited by Sylk; 03-29-2022, 11:00 AM.
                    Software: FStormRender: 1.5.0h | Drivers NV: 456.71 | 3dsMax: 2020.3 | Windows: 10 x64
                    Hardware: Gpu: GTX1080 Phoenix GLH | Cpu: i7-2600k@4.5GHz | Ram: 16GB | SSD: Samsung 860 Pro

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                    • #11
                      I guess you answered my question before I posted, hah! Are you stuck without it or do you have a solution?

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                      • #12
                        Yes I enabled the "process alpha" option but I need it as a pass for this specific purpose. I'm just going to re-render the whole animation. I made the mistake of rendering out a mask instead of an Alpha channel so I don't have the transparency of the glass baked in. That's the reason I wanted to do a seperate Alpha pass, it's a bit faster then fully rendering each frame again.

                        btw I was able to save the beauty pass with an alpha baked in, I just didn't check the Include Alpha option. But still can't extract the alpha from those files.
                        Last edited by Tok Tok; 03-29-2022, 10:56 AM.

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                        • #13
                          What format are you saving in. .EXR with alpha or other?

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                          • #14
                            And do you see the checkered background like in my sample image? If not you aren't getting alpha most likely.

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                            • #15
                              I'm saving PNG with alpha and that's working now. I'm now re-rendering the whole animation.

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