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My question is simple: does Blender support texture where RGB is color, and A is a grayscale texture (not transparency)?

The image file can be PNG or TGA, both with straight (aka unassociated) alpha, and all I want is to extract that alpha, without affecting the color channels.

So far, I have tried every "color space" + "use alpha" setting combination, and none can give me both a straight alpha and correct RGB color:

  • I can pick sRGB/Linear without alpha, then I got RGB channel right, but A channel is all white.
  • I can pick sRGB/Linear/Non-color/Raw with alpha, then I got A channel right, but all black in RGB channel.

And this only affects Render view. Material view is somehow happy either way.

Any clues?

enter image description here

enter image description here

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  • $\begingroup$ similar question was asked here, in 2015, but I should note that I already know this workaround: it basically require you to duplicate the texture file, as color-space and use-alpha setting are per texture, not per image node. blender.stackexchange.com/questions/32450/… $\endgroup$
    – bitinn
    Aug 13, 2018 at 8:23
  • $\begingroup$ other workaround (such as dividing alpha) is not possible here because alpha is 0. and so far I research suggest texture with non-transparency alpha are still unsupported as of blender 2.79 releases $\endgroup$
    – bitinn
    Aug 13, 2018 at 8:24
  • $\begingroup$ my case is also the opposite of this question: where OP wants to apply the alpha mask, which is do-able in Blender. blender.stackexchange.com/questions/104642/… $\endgroup$
    – bitinn
    Aug 13, 2018 at 8:27

1 Answer 1

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This behaviour seems to be internal, so no easy way to modify it. But a way to facilitate that duplication process is to instead of duplicating the texture file itself, duplicating the Image datablock that references the file inside Blender.

  • Create the Image Texture node as usual and duplicate it, and then click the user number to make a new copy of the Image datablock -- they will both reference the same file but have separate Use Alpha settings.

Click to make a single-user copy

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  • $\begingroup$ Cheers, I am aware of this though: see my comment in OP :) $\endgroup$
    – bitinn
    Aug 13, 2018 at 10:49
  • $\begingroup$ You wrote "duplicate the texture file" in the comment, to me that means a file in your HDD. To clarify: image file = file.png | image datablock = image object as seen in the UV\Image Editor | image texture node = cycles node in the node editor. You duplicate the image datablock ("make single-user copy"), not the file. $\endgroup$
    – R. Navega
    Aug 13, 2018 at 12:32
  • $\begingroup$ @RN thx for clarifying, I should have edited that comment, I am aware of both approaches. $\endgroup$
    – bitinn
    Aug 13, 2018 at 13:15
  • $\begingroup$ (for future users: this is what we are talking about, select image texture node, press N in node editor to view properties panel and find this: i.stack.imgur.com/zPKfA.png ), one thing I don't quite like about this workaround: it's quite easy to have used an incorrect source image file as there is no way to view them without expanding properties view. $\endgroup$
    – bitinn
    Aug 13, 2018 at 13:25

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