Textures disappearing when joining objects blender

[barberry]

Hi there,

I’m doing the Blender Environment Artist: Create Your Own 3D Game Worlds. On lesson 8.3, joining the modules - when I do ctrl J to join the plaster and beams, the textures on a few of the objects disappears. It affects all the small beams and the door / window panes on any of the plaster units I try, the small beams go completely black and the door plane goes a dull reflective material. I’ve already separated all the linked objects by object and data. When i try using a different object as the active object, either the same pattern happens, or those items stay but marks appear on some of the other beams and the UV unwrapping seems to shift on others.
Many thanks in advance for any assistance!

[VVruba]

It’s hard to say conclusively what’s going wrong without access to the blend file. It could be UVs getting jumbled up from joining multiple objects, materials getting unassigned from their vert groups or something completely different.

That said, joining objects like that is generally not the best way to go about this. As I’ve not done this course I’m not sure if there is some specific reason for doing it this way but in my personal opinion you would be better served using the parenting system to build up complex structures instead.

Simply make an empty object and assign it as a parent to those objects, then name it something appropriate like "wall_door" or "wall_window". You can then duplicate the empty along with all it’s child objects to build out your structure, then parent that to another empty called "house" or "inn" as an example.

The benefit of that approach is that your objects will be more organized and have a proper hierarchy to them. This will make it easier to edit them in the future or make adjustments. They won’t have to hold all the materials either, just those relevant to each part which would prevent problems like the one you presented from occurring.

[NP5]

Also check there are not duplicate objects just there sitting in the same place and getting rendered over the joined ones.

[Megane_Wang]

Have you ensured to apply all transformations before joining the different items? This part of the course has some repetitive processes and it is not impossible to forget a step. That could be a deformed, stretched UV map due to having forgotten this, as well as a superimposed object as @NP5 said.

[barberry]

thanks all so much!
thanks for the suggestion to parent, I have done that before and also did wonder why that wasn’t an option / wanted to work out what was going wrong but I’ve tried parenting and that is working fine , and like you said it is good for onwards working so I’ll stick with that for now. The course uses blender 3.1 so that might be why it doesnt use it ?
Check duplicates is v good shout I hadn’t thought to try that yet so thought that would be it but there weren’t any spare duplicates, so still not sure exactly what’s going on, but yeah parenting working so will use that!
and yes all transformations were applied. I tried parenting instead and carried on with the course and at a later stage it was mentioned that this can happen when joining, that the UVs change, but they weren’t that severe in the example so wasn’t a big issue, it’s just in mine they were quite extreme!
thank you