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I have a transparent object that I am rendering without any sort of background, ie film is set to "transparent." Rather than have slightly transparent pixels, the alpha channel is black and white, no greys. Is there a way to render a transparent object over a transparent background in such a way that the alpha channel is reflective of the transparency of the object, not just the shape of it?

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  • $\begingroup$ Does your transparent object have varying degrees of transparency? $\endgroup$ – rcgauer Oct 10 '18 at 16:59
  • $\begingroup$ No, but unless I'm wrong about how it works, I'm expecting that it would appear less transparent towards the edges and almost 100% transparent towards the center, much like the fresnel effect. $\endgroup$ – Ben Mora Oct 10 '18 at 17:03
  • $\begingroup$ Are you in Cycles? I am guessing so. $\endgroup$ – rcgauer Oct 10 '18 at 17:40
  • $\begingroup$ Oops... Sorry: My understanding is that the alpha channel's output carries 1 to 0 info on the sum characteristics of the transparent material.... So the % black or white reflects both transparency and surface color of the transparent material. (If you add a noise node to a transparent material's color input, for example, the alpha output reflects the noise -- but in B&W. ) You can use Set Alpha node to adjust these, but I do not believe any edge-like influence is intended... but I can't find 2.78 docs online right now. All have migrated to 2.8, which is cool but not helpful. $\endgroup$ – rcgauer Oct 10 '18 at 17:43
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Not presented as an answer so much as extension of comments above: You can add a fresnel and holdout to your material to generate other alpha-node output characteristics... enter image description here

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