The Projection matrix

On a physical camera, you might have a selection of various lenses with different properties – a wide angled lens for wide shots, or a telephoto lens for zooming in close. The Projection matrix is the way we describe such properties to the XNA rendering system. The Projection matrix describes to the graphics card how to translate (or project) 3D objects onto the 2D viewing area of the screen. The following image illustrates the parameters used to construct the Projection matrix:

The Matrix.CreatePerspectiveFieldOfView() method accepts four parameters that define how our virtual camera will view the 3D scene. The first is the field of view, or viewing angle, that the camera covers. The larger this value is, the wider the angle the camera will display. In this case, we specify MathHelper.PiOver4, which translates to a 45 degree angle.

Note

Angles in XNA

XNA handles all angles in radians. In a full circle there are 2*pi radians. Half of a circle is 180 degree, or pi radians...