Simply adding an image to mesh (UV confusion)

Question

I don't fully understand UV Mapping.

I imagine that the shapes that evolve from the flattened/cut open 3D object, are laid out on a 2D canvas which is the UV Map. You can draw on that canvas, add images and all the things that are within the shapes (unwrapped 3D object) are gonna be shown on the 3D model, where the shapes belong.
But as I understand now, The Map is basically one Image and you lay those shapes on top of that one image.

1. Can I put a second image on there on a specific island?
2. Can I create a separate UV map for unwrapping only a specific part of the mesh?
3. Is a new map created every time I unwrap the object? If yes, how can I mangage all those maps?
4. Does a texture without alpha always cover the whole 3D model?
5. When is a texture from a UV Map activated/rendered? Does that only work via the shader editor?

As an example, how would I put this white logo/lettering on this screwdriver, which I modelled in Blender? Assuming that I have the logo as an image file.

I use Cycles for that project.

^{Click to enlarge}

Answer 1

Easiest way of solving that problem is to

Firstly, Bake the Textures from the modeled object that you've created.

Select the 3d object. And goto "Editmode" and mark seam Ctrl+E-->"Markseam" then U-->Unwrap. Then open your "UV Editor" to check your unwraped mesh.

If you have no knowleadge about unwrapping mesh without overlaping check out this links

Painting a dog with texture paint, TOTAL NOOB

https://www.youtube.com/watch?v=scPSP_U858k

Now, create new Image for your unwrapped mesh to bake the textures in.

Now, goto "Shader Editor" and create new "Image Texture" Node by Ctrl+A--> Texture --> Image Texture.

Now, select the Texture Image that you've created for your mesh, in your newly created Image Texture Node. and Select the just the Image texture "node".

Goto the Scene and select Cycles Engine.

Now, goto the bake menu

Select the bake type --> Diffuse and just check the "color" option.

Now, goto "Object mode" and Hit "Bake" button under bake menu.

------------Wait for it to bake the texture.---------------

Now save your texture and open it in "Photoshop".

Now open both the saved texture file and the logo png file in Photoshop or other photo editing tools. In my case I've used Photoshop to add the logo to the texture.

Now, save the edited texture(or) image file.

Now, if you'd open the edited image/texture file into the blender and plug it to your mesh you'll see something like this.

But I've even created and added a Normal map of the diffuse map to get a bump effect of the logo.

Answer 2

So for everybody looking for a solution for that situation as well. There are two ways (probably even more) to solve it:

1. The one that Akai explains in his post very detailed
2. The one that is explained in this video https://www.youtube.com/watch?v=VnfTSXWF21A

Thanks for the help!