There are no new OpenGL functions used in this tutorial. However, the method used for drawing the shadow needs a little explanation.
One way to produce the shadow is to enable-disable lighting as the facets are rendered. In particular, if it is decided that a facet is in shadow, then we disable the light that is producing the shadow; otherwise, we enable that light. This method is consistent with the concept of a shadow however, it produces a very coarse shadow when the facets are relatively large. This is the case for our board since it is made up of "large" quadrilaterals. Thus, we use a different method in the tutorial.
The alternate is "covering" the board with a large set of points where each point has the shadow color. With each update of the display, we calculate which points are in the shadow and, in turn, render only those point. This technique gives a more effective image of the shadow.