In the workflow of 3D modeling, an important part is dedicated to texturing the 3D objects, that is: to map a 2D image (the image of a skin, of a tissute, of a rock...) on the surface of a 3D model (a man or animal, a piece of clothing, a landscape element...).
The texture, the image which is to be painted on the object, is generally a 2D image obtained from a photo or an external 2D processing software.
But before you can map this texture on a 3D model, you need to know what part of the image should be mapped on each polygon of the model. There are several names, all referencing this correspondance between the faces of the object in the 3D world and the texture's 2D plane: texture coordinates, UV coordinates or UV mapping.
How do texturers produce UV mappings of a 3D model? Until recently, the only possibility was to create them by hand. Regular 3D modeling software (SoftImage|XSI, 3DsMax, Maya,... ) offer some basic tools like planar projection, cylindrical projection or box projection. These operations, applied on a 3D object, provide a starting point to work on the UV mapping.
But these methods produce a lot of waste UVs: a spherical projection is perfectly fit to deal with spheres, but it is not adapted at all to produce UVs from other geometrical shapes. It produces countless problems such as surface stretching, polygon overlapping, triangle flips, starnge perspectives etc... Basically, with these starting bricks, the artist has to move by hand the points of the UV mapping to obtain a decent result - and get rid of overlappings, flippings, and try to handle surface stretching...
This work is long and tedious. With this kind of method, the time it takes to produce a usable UV mapping for a model can range from 1 hour for small models (~1000 triangles) to days for bigger ones (~40 000 triangles). Creating UV mappings for really large models was completely unconceivable, because of the sheer timelength of the process.
Since then, several methods have been developped to produce these UV mappings automatically. The basic idea is to cut out the 3D model, along a cutting line, and then flatten it on the 2D texture plane, opening it along this cutting line - much like cutting out a football and flattening it on a table.
Unfold3D was one of the first automatic unwrapper on the market, and is still the best product in its field. Through a simple "cut & click" workflow, it produces in seconds hig quality UV mappings, usable right out of the box. It uses a top of the art algorithm to minimize polygon distorsion, which produces results far better than any handmade UVs. The time to produce UV mappings is taken down to minutes. Texturers can now forget about the tedious job of creating UVs, and concentrate on the texture creation part.
