So, now that you understand coordinate systems, let's talk about cameras. As mentioned previously, drawing a scene in 3D is much like recording a movie with a handheld camera. You have to define where the camera is located, what it's pointing at, and various other properties.
These properties are stored in a
Matrices are fairly complex mathematical entities that are well beyond the scope of
this chapter and the book in general. Suffice it to say that matrices are at the
heart of almost everything you do in 3D graphics. Fortunately, XNA handles all the
hairy matrix details behind the scenes, and at this point, you really don't need to
concern yourself with how it all unfolds. For now, just understand that a matrix or
two can represent a camera.
There are two
Matrix objects that make up a
camera in XNA: the view and projection
matrices. The view matrix holds information that determines where the camera sits in
the world, what direction it's pointing in, and what its orientation is. The
projection matrix holds information that determines properties of the camera based
on the angle of the view, how far the camera can see, and so forth. This matrix
represents the transformation from the 3D world to the 2D plane of the
To create a view matrix, you use a static method from the
Matrix class called
This method returns a
Matrix object and accepts
the parameters listed in Table 9-1.
Table 9-1. Parameters of Matrix.CreateLookAt