As you probably know, a computer screen creates a two-dimensional image. You can't do anything to change this, but if you are clever, you can create the illusion of having a three dimensional image. This task is very tricky, but fortunately many scientists have worked on this problem for years and have found ways to give good illusions of three dimensional images. Some important things to create this illusion are providing accurate shadows and accurate overlapping of objects. If you take any art classes, you might ask your art teachers about the tricks that painters use to create the illusion of three dimensional images. Many of these tricks are also used by computer programmers.

Fortunately for us, we can now buy many computer programs that allow us to easily create these "three-dimensional" images. Many of these programs let you say things like: Place a green cube at the coordinates (x,y,z) and Place a red sphere at the coordinates (x2,y2,z2). These programs will automatically make a nice image for you. Unfortunately, some of these good programs are expensive and require expensive computers, so your program might not be very good at doing three-dimensional graphics. If this is the case,I have a good project for you to think about. Think about a set of railroad tracks which are going away from you. Think about what they would look like if you were standing on the tracks looking into the distance. The tracks come together, right? Well, using a simple program that lets you draw lines and boxes, you can draw tracks that look three-dimensional. This project will be very helpful in understanding some of the important issues in 3-D computer graphics.

The basic idea for 3-D images on a computer is to show a projection of a 3-D model on the 2-Dscreen. Essentially, this is done using a bit of trigonometry... For example, if you draw a cube in3-D, you use a perspective transformation to find where the 2-D image should be. This topic is very deep since so much money has been spent on 3-Dgraphics... A good place to start is the simple perspective drawing books -- but if you want to know how to make real 3-D images for a computer, I recommend:

3D Computer Graphics (AlanWatt) from your library.
On the net, graphics will indeed give you a bunch of pictures, but not the techniques. You might take a look at James Blinn's homepage as he was a pioneer of 3-Dgraphics on computers.