When mapping an image onto an object, the color of the object at each pixel is
modified by a corresponding color from the image. The image is called a texture
map and its individual elements (pixels) are called texels. The texture map
resides in its own texture coordinate space, often referred to as (s,t) space.
Typically (s,t) range from 0 to 1, defining the lower and upper bounds of the
image rectangle.