Lighting: The Easiest Thing That’s Tough - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 115

In the world panel, enable Environment Lighting and set it to Approximate. Use the defaults from the last
section: error at 0.5, Pixel Cache enabled, correction at 1.0, and Color set to Sky Color. Reduce Energy
to 0.5. Why not use it at full strength (Energy at 1.0)? We will be using a sun lamp for the direct illu-
mination, so the environment lighting will only fill in the places that the sun don't shine. Ahem. How
bright should an area be that is in shadow, but fairly out in the open (i.e., the ground under the table)?
0.5 is a good starting point.
Before we even render this, let's set up the sky so that the Sky Color option makes a difference. Above
the Ambient Occlusion panel on the World Properties is the main World panel. Color pickers allow you
to set both the horizon and zenith (top of the sky) colors. For this test, I've chosen a light blue and a
Figure 5.21 The 3D structure of this setup.