The Rendering Pipeline - Introduction to 3D Game Programming with DirectX 9.0 - page 70

parts. The part inside the frustum is kept, while the part outside is
culled.
Figure 2.13 shows the three possible scenarios.
Figure 2.13: Clipping geometry outside
the viewing volume
2.3.7 Projection
In view space we have the task of obtaining a 2D representation of the
3D scene. The process of going from an n dimension to an n - 1 dimen-
sion is called projection . There are many ways of performing a projec-
tion, but we are interested in a particular way called perspective
projection . A perspective projection projects geometry in such a way
that foreshortening occurs. That is, objects farther away from the cam-
era appear smaller than those near the camera. This type of projection
allows us to represent a 3D scene on a 2D image. Figure 2.14 shows a
3D point being projected onto the projection window with a perspective
projection.
Figure 2.14: Projection of a
3D point onto the projection
window
The projection transformation defines our viewing volume (frustum)
and is responsible for projecting the geometry in the frustum onto the
projection window. The projection matrix is complex and we omit a