Single Object - Multiple UV Layouts vs. Multiple UV Maps

Let’s say I have a single object with various complex meshes within it. What’s the difference between…

  • An object having multiple UV Layouts (on a single UV Map) assigned according to designated material
  • Having multiple UV Maps within the UV Maps list and having a Layout per UV Map

When should someone use one approach over the other? Is one a better approach?

Hopefully I asked that correctly.

Every UV map contains coordinates for everything. Assigning a material to some of the faces is one way to limit where the material assigned texture shows up when it uses UV mapping. It’s also a very straightforward and easy. Limiting it with another UV layout is needed when the texture doesn’t follow face boundaries, or the material has multiple material assigned textures which need a different layout.

Ok. I understand this I believe. This is where you would have materials assigned to certain parts of the mesh and by making those material assignments actively selected, it limits which UVs are visible. Correct?

This I’m a bit unclear about. Is there an example (like a YouTube video) that demonstrates this?

Also, what about my second example given? Where you have multiple UV Maps via the UV Maps Panel. What is a practical example of using this panel? At first glance, I can see that the camera icons allow toggling of active render map.

No. You have a mesh type object, it consist of a mesh or multiple mesh parts. UV maps are a 2D representation of those meshes, and each UV map listed in the UV maps panel contain coordinates for everything. Materials are assigned to faces, and the material assigned textures can use UV coordinates for mapping. The UV coordinates exist whether there’s a material or not.

The mesh faces and UV’s coexist, that’s why they’re in object data properties. There’s no UV coordinates without a mesh. Assigning different materials to different parts of the mesh can limit the visibility of the textures.

Materials are assigned to faces, but the textures it uses can’t always be limited to those faces. A wood material with a text on it for example. It would be one material with two material assigned textures: first is a wood texture using one UV map, and a mask map for the text on top of that which uses a second UV map because it has to be mapped differently.

Or, having different materials but they share a texture. A piece of wood with a silver stripe in the middle, and a text going over all of it. The wood parts could use same texture and same UV map, but the text would be likely to need another UV map so it can be positioned, scaled and maybe rotated in place, without messing up the coordinates already used for the wood texture. Both materials would share the texture for the text.

UV maps panel is for managing different UV maps, again each containing coordinates for everything, but allows to have different layout for those coordinates when needed. It’s limited to 8 maps.

Sometimes you’d also define a specially laid out UV map (often purely rectangular for machined/lathed mechanical parts) to be used for aniso tangent, which wouldn’t be very usable for anything else.