Culling Polygons According to the Normals

The removal of a polygon from rendering is called culling. Culling can occur on an entire polygon or just one side. The side that is removed during the culling process is called the backface and it is the opposite side of the polygon to that from which the normal is projected.

In the next practical exercise, we will explore how normals are used to display these types of images.

Let’s do it…

So far, the polygons we have been rendering have had textures on both sides, unbeknownst to you. Now it’s time to take a look at what’s going on both sides:

1. From GitHub, download a copy of plane2.obj from the Chapter 11/models folder and place it in your project’s model folder.
2. Make the following changes to ExploreNormals.py:

   from Cube import *

   ..

   objects_3d = []

   objects_2d = []

   cube = Object("Cube")

   cube.add_component(Transform((0, 0, -3)))

   cube.add_component(Cube(GL_POLYGON,

      &...