Faking 3D

When you look at the map in the previous section, you will notice that the map is a two dimensional structure. The truth is, the 3D environment that you wander through is actually a two dimensional environment that is cleverly disguised to look like it is three dimensional. Due to the fairly structural nature of walls, with this game it is very easy to take the two dimensional map and extrude the walls to form the three dimensional maze. Purists will point out that this is not real three dimensional, but I have walked through cubicle mazes, and most of them in the real world do look just like the game does so I am not sure why purists would make such a big fuss over such a minor detail.

Of course, when you get right down to it, even if I was using a map that was made up of true three dimensional polygons, the monitor I am using (and unless you are reading this book well after it was released) is two dimensional. Even so called true-three dimensional games are two dimensional on my monitor. Why the game is considered to be three dimensional is because of the way the image looks.

There are all sorts of visual clues that the human eye uses to process an image for depth information. What is really interesting is that a lot of our depth perception is based on our knowledge of the world. This is the reason that optical illusions (such as the size of the moon) exist. The most important things that are used are size, shape, and lighting.

The size of an object within a picture helps us determine how far away the object is. This is where our knowledge of the world comes into play. We use our experience about how big an object is to help us figure out how far away the object is. Without some knowledge of the size of an object, figuring out the size of something based on a picture is hard to do. This is the reason you will see well known objects in pictures of lesser known things. For instance, a coin is often shown beside a computer chip and people are often shown in front of huge structures. This allows the person looking at the picture to better grasp the scale of the object being shown as they know how big the object being compared to is.

When I say shape, I am not talking about the actual shape of the object, but the visual shape of the object. As you know a cube has six sides with all the sides being the same shape and size. Yet, when you look at the cube (especially larger ones) you will notice that the sides of the cube all look different. This is because parts of the cube are further away than other parts. This change in how the shape looks is called perspective and is covered in a huge number of art books.

Finally, lighting. On the surface lighting may not sound like it is that important to depth perception, but it is actually a very significant part of how we determine the shape of an object. This is because the shape of an object determines how light bounces off of it. This can be fairly complex and there are entire volumes dedicated to this subject, but a simple example can explain a lot more then a detailed boring description. If you were able to somehow remove shadows and view objects as a solid color, then a disc and a sphere would look identical. By simply adding shading to the color, you can suddenly tell the difference between the disc and the sphere. This is because the different points on the sphere have different brightnesses due to how much light bounces off the object and how much of the light bouncing off of an object bounces into your eyes.