Basic question about UVs

I’m at the very beginning of my journey of learning about modelling/texturing/UVs, so this is probably a **really **basic question.

I’m looking over some of the free content (from the Infinity Blade Grass Lands pack) to see how people who know what they’re doing actually texture and UV their stuff. I’m looking at a staircase, and very confused by the UV layout:

Why are there UVs going off the UV map? What are these red UVs?

I’ve been following some basic ‘modelling for games’ courses etc. and thought it was pretty important to have all the UVs in 0-1 space, carefully laid out? What’s going on here? I understand that there are many UVs overlapping here because they’re pulling from the same part of a texture map containing textures for various other objects (to cut down on quantity of texture tiles), but I don’t understand these UVs going off the edge of the map.

I’m sure this is something fundamental/basic, but it’s not something I’ve seen explained anywhere.

The red just means it’s going off the main 1:1 grid. Which is fine for tiling textures.

Tiling textures don’t need to remain in the 1:1 space, but uniquely baked textures do (generally).

For textures you don’t have to keep it in the 0-1 space. For example, sometimes you might control tiling using the UV’s rather than changing the tiling in the material. For lightmaps you do need to avoid overlapping and keep it in the 0-1 space but you would put that on the second UV channel if your main UV’s don’t follow that guideline.

dont forget that uv islands in lightmaps cannot be mirrored either :slight_smile:

Right, they should not be inverted (facing down)

Ah, OK! So does that mean that this UV map is having no effect on the appearance of the texture then? Where is the tiling for something like this controlled? There’s no Texture Coordinate node in the material.

In that specific object the overlapping does not affect the appearance negatively. There isn’t really any tiling there, they’re mostly positioning the UV’s, they have some loops on the mesh so that they can change the UV mapping for each brick.

ue4 textures tile automatically unless otherwise specified in the texture options in the texture viewer.