What is a UV map?

- In my experience, one of the most difficult things for someone new to 3D animation to get their heads around is UV mapping. It's hard to find anything in the real world that you can compare it to. For 3D modeling, you can compare it to building with blocks, or maybe molding clay. And of course, the process of lighting in any 3D animation software has a lot of similarities to real world lighting. But UV mapping, what is it? Well, it's the process that makes a two-dimensional representation of the surface of a three-dimensional object.

It takes the topology or polygons of a 3D object and lays them out flat in two-dimensions. Kind of like cutting the edges of a cereal box and spreading it out flat on the kitchen counter. The UV map is a template, and when we take it into an image manipulation program like Photoshop or Gimp, it can tell us exactly where we need to place our image, so that when we bring it back into Blender, we can wrap the image back over our 3D object.

If we place an image at a particular place on the UV map, it will then be mapped exactly to the corresponding coordinates on the 3D object. But why the funny name? Why UV? We're dealing with two dimensions, a horizontal and a vertical axis. Why not use X and Y to describe them? Because X and Y were already being used to describe two of the dimensions in 3D space. Any other two letters would have worked, but U was chosen to signify the horizontal axis, and V the vertical.