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UV Image Editor overwrites Cycles materials
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I believe this was reported before, but I'm opening it again in hopes of further investigation.

--- Operating System, Graphics card ---
Windows 7. 2x GTX 680s

--- Blender version with error, and version that worked ---
Blender 2.66a

--- Short description of error ---
The image editor overwrites the Cycles material's textures.

The UV Image Editor is linked to the material nodes, so if a new image is selected in the Image editor, it overwrites the texture in the cycles node setup.

This is bad for multiple reasons:
-Artists often want to see the UV layout on a blank canvas but doing so deletes the image from their material nodes
-Materials often have multiple textures. Deleting or overwriting textures unknowing, causes a constant frustration of finding the missing texture and correcting it.
-When multiple UV layouts are in use, blender doesn't know which layout is for which texture and so can just overwrite everything
-Confusing to new users who aren't sure why their material keeps rendering purple when previously it rendered fine.

I honestly think that the UV image editor should be completely separate to the Cycles material nodes, and not linked in any way. It just causes more problems than it solves. The image editor is often used by artist as a canvas to test and experiment layouts with textures. So having it overwrite materials is a frustrating and unnecessary annoyance.
I've heard from many other blender users like Reynante Martinez who have the same thing.

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
1. UV unwrap a cube
2. Assign a material with a texture in the node setup
3. Delete the image from the UV image editor

The node setup will have deleted the image from the setup, which is not necessary what the user wanted.

Event Timeline

I've had the same problem many times too. It breaks cycles materials and makes working in the image editor a pain (while working in cycles).
Having the the texture-nodes linked to the image editor creates more problems then it solves
I'm guessing that the reason it was rejected the first time was because this is technically not a bug, just a different behavior..
But yeah, I support this one!

Brecht, what's your opinion here?

Ok, I've removed this system now, the image displayed in the image editor is now completely decoupled from the material. That's not ideal either I think but probably the lesser of two evils, I haven't found a better solution yet.

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Resolved.Apr 15 2013, 8:06 PM

That's perfect Brecht! Thank you!
Leaving it as completely unlinked to the material will be just perfect. As Kjartan said, having it linked just causes more problems than it fixes.

So I honestly think it's just better to just keep them separate, as it has been in the past.

Anyway, thanks so mate. To me this is the most excited bug fix in ages! :)

I bumped into this cause i found the other method working finer. When i go into edit mode i want to see how the uv is on the texture. Now each time i want to edit or redo something i first need to check which texture it was. Therefor you also need to have the compositor open, so more space is lost, ofcourse we can [space] to focus a window. I yet find the method of relinking a texture each and every time again very double.

Why cant it be linked without being influential to a material. I mean it can be linked to a node as a copy. BI it can be linked without any influence or is this cause the materials work different on a mesh when rendered.

Such questions better be asked at bf-funboard mailing list, not in the bug tracking system.

Hi brecht. Even in 2017 me and some others stumble over this behaviour and I want to try another solution myself. I am an experienced software developer, though never done anything in blender sourcecode so far.

Can you lead me in the right direction which parts you changed back in 2013? I cannot find your commit. Maybe you have a patch flying around?

That would help a lot, thank you in advance

It was commit rBceb61eb14d86: Fix #34978: for cycles, images displayed in the UV editor where coupled to the….

Maybe the right solution is to make it linked again, but communicating it better in the image editor header that changing the image means editing the material, showing the material icon or name.