Basic Help diagnosing the UV Editor Box (Maya)

muddymink

Hello! I am a self taught 3D artist, so I've never had a good explanation on the simple subject of UV layout editor. 



I understand the UV's are laid out in the top right section of the UV editor, but what about the rest of the space we are provided? (Circled in Blue). 
As far as my understanding goes, this is used for adding different materials? Or is that wrong? It may not even serve a purpose at all!

If anyone would be willing to explain some of the main uses for these 3 extra spaces in the UV editor, I would really appreciate it! Thank you!

(I've tried googling this, but I was unable to find anything of use!)

throttlekitty

The area in the upper right is known as the 0-1 space: the grid starts at 0,0, and ends at 1,1 in the upper right.

The rest is extra space. If you do View>Grid [options], you'll find that you can expand it as much as you want. It's helpful for a lot of workflows to visualize the grid, such as tiled textures on very large objects, working with UDIM tiles, offset shells for baking, etc. Another common use (for me at least) is when I have a lot of textures on an object leaving me with a big overlapping mess. I'll usually move sets of UV shells a whole grid unit to the right or whatever so I have a clean space to work in for each texture.

At 10x10, it looks like this, it adds both vertical and horizontal rows even if I'm only using the upper right quadrant.

Axi5

As throttlekitty says it's just extra space and for game models you will only really care about the upper right part. In VFX they use UDIMS which go off the 0-1 space but we don't typically use those.

As for your questions on materials, no they're handle on a polygon object basis not specifically a UV basis. Picture a polygon as an object filled with metadata, it contains:
Geometry:
    An ordered list of vertices
    Ordered list of normals
    UV texcoords for each vertex
    Possibly other attributes such as blend shapes etc.
Material:
    Shader meta data (literally just the name of the shader applied, the actual shader is contained elsewhere)

That's kinda it. Multiple materials on the same object are technically broken apart before it gets to the GPU.

The point is you can see how the shader/material is separate metadata from the geometry, the two don't share a direct relationship, they just tell the software what they are.

What happens when you put UVs outside of the 0-1 space? Simple:
It acts as though it's actually IN the 0-1 space. Take that loosely because the vertex texcoords are still technically less than or greater than the 0-1 area and you can do some effects with this but when you apply a texture it'll appear as though it's still being affected. This is actually due to texture tiling, it's a per-texture object definition that most game engines leave enabled by default. I.e. by default if you apply a texture and then move the UV shell anywhere you want, it'll only ever offset the texture, you'll never run out of texture. However, if you move a UV shell outside of the 0-1 area and then disable tiling on the texture that's applied, then depending on what tiling mode you selected you'll either see a stretched texture across those UVs or just a flat colour.

pior

On top of all the great explanations above, I would add that one way to understand this seemingly "unused space" is to force oneself to *not* rely on too many analogies when trying to understand any CG topic.

For instance : when starting out with UV mapping/unwrapping, you might have heard things like "imagine an orange that you peel. Uvs are just like an orange peel that you draw a texture on then put back on the orange". While this is great in order to initially grasp the concept in layman terms, the analogy quickly breaks down because then the rest of the UV space doesn't seem to make much sense (hence this thread).

But if you think of the UV space (UVW to be exact) for what it actually is (that is to say : a coordinate system with x y and z, with z not being shown), then it makes total sense that values can go below than 0 and higher than 1 ... because that's what a coordinate system does, regardless of what we commonly decide to use the 0-1 range for. The Maya UI designers simply thought that users might find it handy if the 0-1 range was highlighted, because it is universally accepted as the range we map textures to.

As explained by the posts above  there is an infinite number of uses for this seemingly unused space.

I hope this makes sense !