Document setup work.

main.py

@@ -803,11 +803,19 @@ def setup_fog():
     """ Configure the OpenGL fog properties.
 
     """
+    # Enable fog. Fog "blends a fog color with each rasterized pixel fragment's
+    # post-texturing color."
     glEnable(GL_FOG)
+    # Set the fog color.
     glFogfv(GL_FOG_COLOR, (GLfloat * 4)(0.5, 0.69, 1.0, 1))
+    # Say we have no preference between rendering speed and quality.
     glHint(GL_FOG_HINT, GL_DONT_CARE)
+    # Specify the equation used to compute the blending factor.
     glFogi(GL_FOG_MODE, GL_LINEAR)
+    # Set the fog density.
     glFogf(GL_FOG_DENSITY, 0.35)
+    # How close and far away fog starts and ends. The closer the start and end,
+    # the denser the fog in the fog range.
     glFogf(GL_FOG_START, 20.0)
     glFogf(GL_FOG_END, 60.0)
 
@@ -816,15 +824,24 @@ def setup():
     """ Basic OpenGL configuration.
 
     """
+    # Set the color of "clear", i.e. the sky, in rgba.
     glClearColor(0.5, 0.69, 1.0, 1)
+    # Enable culling (not rendering) of back-facing facets -- facets that aren't
+    # visible to you.
     glEnable(GL_CULL_FACE)
+    # Set the texture minification/magnification function to GL_NEAREST (nearest
+    # in Manhattan distance) to the specified texture coordinates. GL_NEAREST
+    # "is generally faster than GL_LINEAR, but it can produce textured images
+    # with sharper edges because the transition between texture elements is not
+    # as smooth."
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
     setup_fog()
 
 
 def main():
     window = Window(width=800, height=600, caption='Pyglet', resizable=True)
+    # Hide the mouse cursor and prevent the mouse from leaving the window.
     window.set_exclusive_mouse(True)
     setup()
     pyglet.app.run()