- What is a texture and what is its purpose?

Textures are mainly used to give a realistic (non-flat) appearance to 3D shapes, without the need for the huge memory that would be necessary to manage very small details. In order to do so, you will stick plain pictures (generally saved in the GIF or Jpegs formats) on 3D shapes.

- How can you use square pictures on 3D shapes?

A texture, as any digital picture, is basically a rectangular and flat shape. The problem, of course, is to put it on a 3D form that will not always be neither flat nor orthogonal.

To do so, you'll have to use a technique rather similar to what you would do to stick square posters on irregular walls and ceilings: fold the poster around the angles, cut away some parts to transform rectangular shapes into polygons or circles, etc.

- How can texture coordinates and 3D coordinates be put together?

You already know that you can describe the faces of a 3D shape by the definition of the vertices in its angles. In a rather similar way, you will define some vertices on the picture used for the texture. If you give corresponding numbers to the vertices on the shape and to the ones on the texture, you'll only have to let 3D programs do the rest (that is: put in perspective the small portions of the picture defined by your vertices).

- How do you define texture vertices?

The main difference between common 3D coordinates and texture coordinates is that you will work in two dimensions, instead of three. Another difference will be that you will not work with measurement units such as millimeters or inches: you will use proportional references. The lower left corner of the texture is always referred to as {0,0}, and the upper right as {1,1}. Please notice that it will be the same whatever the proportions of the picture can be; no matter whether the picture you use as a texture is a landscape or portrait rectangle, you'll always have to think of it as a square.

In three dimensional systems, coordinates are generally called x, y and z. In the two dimensional and proportional system used for textures, the coordinates are generally called u and v (u for the horizontal one, v for the vertical).

- Can a texture be put on any shape?

Absolutely. But of course, putting flat pictures on round or irregular shapes can sometimes be rather uneasy. Imagine Michelangelo trying to put flat pictures of saints and prophets on the ceiling of the Sixtine Chapel. Well, you will have the same type of problems.

- The keywords for textures in the CBB format

- Putting a texture on a square shape

- Using a texture various times on the same shape

- Graphic formats, syntax and memory problems