Also, after marking the seams, the
smart uv mapping option is missing.
So how can I unwrap all these objects in one
In Blender 2.8 and beyond you can enter edit mode with multiple objects selected.
Before Blender 2.8
Simple answer: "you can't"
Because a UV map pertains to each individual object, and only shows in the UV/Image editor while in edit mode, you cannot combine UV maps, or see multiple maps at the same time. (You can only enter edit mode for one object at a time.)
Longer answer: "you don't have to"
Most likely, your best solution is to select all the meshes (not cameras or lights) and press ctrl+j to join them into one mesh. Now you can unwrap them all as if they were one mesh, because they are.
Tip: You may want to reset the origin after doing this. (ctrl+shift+alt+c) -> "Origin to Geometry"
There are also some add-ons that help with generating UV maps that fit with others in the scene, for creating one large texture for all objects, instead of many different textures for each object. Try pressing ctrl+alt+u and typing "UV: Texture Atlas" in the add-on search box. This might help you.
Simple answer: Yes you can!
There is a free addon called 'Multi Object UV Editing' which you can download from github at https://github.com/ndee85/Multi-Object-UV-Editing I am using this addon myself, it works like this: Select multiple objects and press the 'Multi Object UV Editing' button from the tool panel in the 3D view.
It will then temporarily combine your objects into one and open the UV editor as one. Once you are done editing and switch out of the edit mode (tab key) it will transfer the UV changes to the previously selected objects. It's pretty seamless.
There is also a way to do this without add-ons.
- Simply select all the objects you want, the last one should be the one that you want to edit. Then go into Edit mode.
- Then, in the UV Panel, go to the menu "View" and check "Draw other Objects"
There is a tutorial on Youtube as well: https://www.youtube.com/watch?v=rbJbZU3B-Vo
I choosed all objects in "Blender 2.8" switched to edit mode, and chosed all of faces by pressing "A" key. Then i and unwrapped just like unwrapping 1 object.
I guess 2.8 suports uwrapping and displaying all chosen objects at the same time.
I hope this action was not a glitch :)