Hello. I just wonder is there any? For example i have two different objects and i want to unwrap them into one UV-map without joining objects themselfs.
Thank you, but it seems this add-on is for creating lightmaps, while i need to combine normal maps.
I just got an idea.
What if i unwrap all objects one by one, then join them, and pack (Ctrl+A, Ctrl+P) all UV-islands, so they don’t intersect. After this, i split objects. It will give me single objects, each with its own UV, but not intersecting in common UV space. So i can bake normal maps, AO-maps, all that stuff one by one.
Then i join all this maps in Photoshop, using overlay mode, which is quite easy.
And then i join objects again and set this merged map from PS to joined object.
I tried it with two objects and it seems works fine.
If it works, great. The exception is normal maps. You can’t edit them as images since they don’t contain color data. It’s vector data encoded and stored in image channels.
If you have a normal map plugin for photoshop that can combine normal maps, that’s fine, but using tools and modes on a normal map that changes the original “color” values (such as overlay) will just mess it.
I guess i can mask base color (128,128,128) cut off unnecessary parts, and then just combine them all, without using overlay. But in past i remeber video tutorial where they used overlay to make normal map clearer. They just duplicated layer, then used overlay mode to make all details more visible. It looked great.
I know that normal map contains not color, but verctor data, and painting it is not good idea, but sometimes it works fine, especially if i need to get rid of small artifacts. May be human eye can’t see this slight differences.
For example this is my normal from one object
and this is combined normals from two objects (using overlay)
i, presonally, can’t see color differences, which would ruin normal map.
UPD: May be i shall use Multiply mode instead of Overlay? Multiply, seems doesn’t change colors, just copy objects on both layers.
Ill take a look at both images!
Thank you, i’ve already seen this great video some time ago, and i remember that he strongly doesn’t recommend to manually edit normal maps. But anyway, for the sake of speed many professionals often do manual editing, as far as i understand. Anyway, thank you for answer.
I’ve just found such tool - a prefect solution for baking different objects’ maps into one, combined UV-space. And this tool is - xNormals itself 
No need for Photoshop at all.
The algorithm is:
0) Create texture in UV-editor (4k, 2k or else). For example “common-uv-space”.
- Create two different objects in Blender, and UV-unwrap each of them into the same texture, which is “common-uv-space” in our case.
- Join objects and go to UV-editor. You will see all UV-islands from both objects, but mixed and overlapping. Press Ctrl+A, then Ctrl+P. Now all UV-islands proportional and don’t overlap.
- Now split objects. Just select that part of mesh which was one object (You can use “L” hotkey) and press P -> Split by selection
- Now you have two objects again, with their own UV-maps but thier UV-maps will not overlap in common uv-space.
Go to xNormals.
- Load both objects high-poly copies
- Load lowpoly objects
- Set-up your texture size (same size as your common-uv-space).
- Set up axis proper direction, which for Blender is X+ Y+ Z+
- Click “Generate maps”
xNormals will combine maps from your objects into one single normal map. Now you only need to join objects again and set up this texture as your normal map.
For me it was a great help, since baking normals from objects with lots of intersections and complex geometry is enormous pain in the ass. But now we can split every complex object into more simple objects and bake them one by one without any problems.