This step turns 3D objects into 2D objects. There are several types of projection. Perspective projection models an eye looking at a solid structure and will make near things larger and far things smaller. Another option is to use a parallel projection, which means near and far objects are the same relative size on the screen. While parallel projection does not reproduce the way humans see, it can be used to provide better comparisons of size on the screen.

How many floating point operations do you think are required to perform the pipeline steps up to this point? Most steps were matrix multiplications or addition operations without much variation. The computational intensity of these steps depends on the number of vertices and polygons. That dependency on the polygon count sets these geometry processing steps apart from the next step.