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Alpha channel of Textures can't be deactivated in UV Editor
Confirmed, NormalPublic

Description

System Information
Operating system: Windows10
Graphics card:Geforce GTX 970M

Blender Version
Broken: 2.91.0
Worked: 2.83.0

Short description of error
When you load an Image/Texture with an alpha channel in the UV editor, you can't turn the alpha channel off anymore, the image will stay black.
It worked in older Versions from 2.80 up to 2.83, there you only have to click on Color in Display Channel options.

Only areas that aren't black in the Alphachannel will be visible, in my examples I work with textures that need an all black Alpha channel.

Exact steps for others to reproduce the error
just load any Texture with Alpha channel in UV editor viewport

Here an Screenshot from Blender 2.83.0 where it worked

and here an screenshot of Blender 2.91.0, the same Texture is used, I also tried different settings under Image, but nothing works

Event Timeline

RH (wolfv2) updated the task description. (Show Details)
Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Needs Information from User.Jan 20 2021, 2:27 PM

Is this only happening for DDS textures?

We already had rB0badb7f82dd4: Fix T80998: DDS Image files are not displayed correctly, but I cannot reproduce this in current master and 2.91 release.
Here is a dds with alpha that I used:

Does this work for you?
If so, please share the dds that fails.

Please also check this in a fresh build from https://builder.blender.org/download/

RH (wolfv2) added a comment.EditedJan 20 2021, 3:59 PM

Thanks for the fast reply

Is this only happening for DDS textures?

It also happens with .PNG and .TGA format.

Here is a dds with alpha that I used:
Does this work for you?

The Blender Desktop Logo image does work properly in all versions, I checked it out in GIMP to see if there is any difference.
I tried different compression types and one without on my texture, but that didn't change anything.

If so, please share the dds that fails.

In this one I made some parts of the Alpha channel white, to make it better visible

I made tests with the 2.83, 2.91.0, 2.91.1 BETA, 2.92.0 BETA and 2.93 ALPHA versions
only in 2.83 the texture is shown correctly with click on Color in Display Channel options.

Blender version: 2.83

Blender version: 2.91.0

Blender version: 2.91.1 BETA

Blender version: 2.92.0 BETA

Blender version: 2.93 ALPHA

Philipp Oeser (lichtwerk) changed the task status from Needs Information from User to Needs Triage.Jan 20 2021, 7:00 PM

I can reproduce the behavior.

It also happens with .PNG and .TGA format.

Can you provide an example for this as well? How did you create those image files that are affected by the problem?

Robert Guetzkow (rjg) changed the task status from Needs Triage to Confirmed.Jan 21 2021, 12:11 PM

While I am on shaky ground in regards to associated vs unassociated alpha (if that even has to do with the issue), I think there is indeed something wrong:

  • If I set the Alpha mode to None on Hull_Armor_Thick.dds, blender does not seem to ignore the Alpha channel (instead, this seems to be the case for Premultiplied Alpha mode?
  • sidenote: I am getting the following for any dds texture:

Unable to find a suitable DXT compression, falling back to uncompressed.

RH (wolfv2) added a comment.EditedJan 21 2021, 2:45 PM

Can you provide an example for this as well? How did you create those image files that are affected by the problem?

I personally use GIMP in the newest version 2.10.22, but that image wasn't made by me but by someone I know of that he is using Photoshop.
It regardless affects all textures, made by me or others using different tools.
The Compression type we use is DXT5, but I tried without compression too and well Blender 2.8 builds have no problem with compression types.

here the same texture but as .png and .tga (exported in Gimp with standardsettings)


Edit: with the right node setup the textures work fine in 3d view, just not in UV Editor wich makes working on UV maps not possible. In this case tileable textures are used quite often and you have to place UVs accurately

The PNG is displayed correctly. The pixels where alpha is zero also has RGB set to zero, hence it displays pure black in these areas when viewing the color channels.

sorry for double Post, I made some more tests with the Blender logo image provided by Philipp.

This one I did export with DXT5 compression like I use and it works without problems in UV editor.

This one I did export with an all black Alpha channel and now it has the same issue like the Hull armor image posted by me

Another try with a selfmade Alphachannel, made it black with a white horizontal line, so when I make Alphachannels on my own it makes problems in Blender 2.9 Builds, but it works in Blender 2.8 builds

here the texture exported in GIMP newest version, I hope this will help

I am also having this problem. Tried with .png and the thought at first that the png didnt write color values for alpha = 0 but that wasnt the case. TGA also showed the same problem.
The only workaround at the time is to disable alpha in the image properties window to see the individual RGB Channels and enable it when you want to view Alpha seperately.
Is someone working on this? It's pretty inconvenient for our current workflow and hopefully easy to fix.