Figure 1-1-1 Two-dimensional drawing


However, when drawing a three-dimensional picture, you draw dots that have both color and depth (z axis) information. Because of this additional depth information, objects that lie behind other objects are partially or completely hidden as illustrated here:

Figure 1-1-2 Three-dimensional drawing


It looks like there is no difference between the two-dimensional final screen and the three-dimensional final screen. But the difference is obvious if you change the drawing order as shown here:

Because the two-dimensional picture does not have the depth information, a picture drawn on top of another picture always wipes out what is underneath it. However, because the three-dimensional picture has depth information, the relationship between two objects holds regardless of the drawing order.

Figure 1-1-3 Differences in the drawing order



1-1-1 More on 3D


Various objects exist in the three-dimensional space surrounding us. As light falls on a three-dimensional object, some parts are lit up and other parts are dark or in the shadows. It all depends on the source and intensity of the light. Also, objects that are far away appear relatively small and appear to grow larger as they move closer and closer. To make objects appear three-dimensional, you need to apply these visual effects.

Figure 1-1-4 3D Lighting Effects


Because 3D graphics data includes three-dimensional information, you can use computer calculations to apply appropriate 3D lighting and perspective effects. Moreover, you can use calculations to rotate and scale objects. These kinds of data manipulations by computer calculation are called transformations.

Figure 1-1-5 Perspective by size



1-1-2 General 3D Graphics Process


The basic 3D graphics process is a three-step process.


1. Create the model

First of all, you need to create the data for the object you want to draw. In general, an object to be drawn in computer graphics is called a model and the set of coordinates and other data belonging to a model is called model data. To create model data effectively, you can use any of the many available 3D graphic tools called 3D Modelers.
You can also create model data on graph paper by hand, and then feed it into a computer. However, this method is complicated and requires a lot of work, therefore it is not a recommended way to create a large model.

Figure 1-1-6 Creating the model data


2. Convert the model data

Next, you need to convert the model data, and place it in the virtual three-dimensional space of the computer. Then provide for the conversion calculations to show rotation, scale, movement, lighting, perspective, and so on. As a result of the conversion calculations, you can display a model that will be viewed from all directions. Moreover, it will be a solid image that has depth as shown by the lighting visual effects.

Figure 1-1-7 Conversion of the model data


3. Display model on TV screen

Finally, you need to send the model data in the virtual three-dimensional space of the computer to the TV screen by way of various software and hardware processes. Ultimately, when the converted model is displayed on a two-dimensional TV screen, the depth (z axis) information is no longer needed. Pixels (picture elements) are displayed on the screen.

This conversion by the computer process has various aspects and produces a variety of effects. For example, you can express a translucent object by taking into consideration the level of transparency when composing a screen.

Figure 1-1-8 Display on monitor