Bitmap materials are used to display a texture map, usually from a JPG, PNG, or GIF image file, on the surface of a 3D object. The alignment of the texture map on a triangle face is determined using what are known as UV coordinates. The name comes from the axes that make up the coordinate space. These 2D coordinates have a range of 0 to 1, and are used to map a triangle face vertex to a relative position on a texture map.

The following image shows the UV coordinates for the vertices used to define the triangle face we created earlier mapped onto a checkerboard texture map.

The U and V axes work in much the same way as the standard X and Y axes used by Flash. The axis naming is distinct between the coordinate systems to distinguish UV coordinates, which plot points on texture maps, to XY coordinates, which plot points within a space or on the stage. Also, keep in mind that the V axis, which increases as it moves up, is the reverse of the Y axis used by the Flash stage and the Flash drawing routines, which increases as it moves down.