A computer-generated 3D model is not really finished and ready to render until it has got some color and information about the bumpiness or smoothness of its surface. As we embark on this stage, you need to be aware that each application has its own way of dealing with color and light and sometimes uses the same name for things that are completely different in other applications. But that is just a matter of words andmechanics. The basics of input to output or what you must add to the object to get the image you want remain the same.