This interface enables you to create both full-screen and windowed rendering modes. You can draw geometric primitives or even sprites to the screen. After the environment is set up, the actual 3D graphics processing takes place. Note that you cannot directly access the pixel data that is sent to the monitor, but you can check it for valid formats.
## Simple 3D Graphics
Now that you have created a virtual framebuffer, you can start drawing graphics primitives to the screen. You can choose between four kinds of primitives: points, lines, polygons, and 3D shapes. We will create a program that draws a figure to the screen. For this, you need to define the figure you want to draw. This will also introduce you to the concept of a 3D vector.
In this example, we will simply draw a cube to the screen. To do this, you will define a 3D vector that represents a cube. When you apply this 3D vector to the 3D coordinate system, you get a cube that you can easily draw to the screen. The figure you want to draw is defined by the four vertices that create the cube. The structure of a 3D vector is defined in Table 4.5.
**Table 4.5** 3D Vector Structure
* * *
**NOTE** 3D vectors are covered in more detail in Chapter 4, "Advanced 3D Graphics."
These four vertices form the top and bottom of the cube. You can move the cube around by simply changing the values of the 3D vector. For instance, the _x_ coordinate defines the position along the _x_ axis. You can rotate the cube around its center by changing the _y_ coordinate. This is a really quick and easy way to create 3D graphics.
The structure of a 3D vector is defined in Table 4.5. You can define the length of a vector by assigning a double value. You can also choose between two different coordinate systems: the world coordinate system and the screen coordinate system. The world coordinate system is a natural coordinate system for 3D objects, such as for a cube. This system has three coordinates: _x_, _y_, and _z_. The world coordinate system is important for defining the position of the 3D vector. The screen coordinate system is used for the 3D coordinate system that defines the location in the virtual framebuffer. You can define the position of a 3D vector
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