UV mapping

UV mapping spreads the surface of a 3D object out flat, much like opening up a cardboard box. Every face takes up a place on that flat layout, whose axes are called U and V, since X, Y and Z are already used for the model’s space. Whatever part of the texture falls on a region of the layout is what appears on the matching part of the model.

Why it is needed

For walls and floors, simple projections (planar, box, cylindrical) are usually enough. On a sofa, an organic sculpture or a curved piece of furniture, though, the texture stretches, slides or breaks at the seams. Good UV mapping prevents this: seams are hidden where nobody looks and the texture keeps an even scale everywhere.

Practical points

• UV islands should not overlap, especially if a lightmap will be baked.
• Leave enough padding between islands.
• Give important parts close to the camera more room in the UV layout.

In architectural visualization, most building elements are handled with simple projections. UV mapping comes into play mainly for furniture, accessories and custom objects, or when a downloaded model’s texture looks distorted.