Overview of Materials in Cycles - Blender 2.6 Cycles: Materials and Textures - page 20

Setting the World material
In this recipe, we'll see the properties and the settings of the World window in Cycles.
The main characteristic of the Cycles World is that it can emit light, so it practically
behaves as a light source. Actually, its effect is the famous "Global Illumination" effect.
As in Blender Internal, it is considered as a virtual dome at a large distance from the
camera and never touching the scene's objects. Nothing in the 3D scene can affect
the World . Actually, only the World can emit light on the scene and on the objects.
Getting ready
1. Open the start_04.blend file and go to the World window under the
Properties panel to the right of the interface. This is where we see the
usual Use Nodes button under the Surface tab.
2. Although no node system for the World window is set by default, the
World window has a dark medium gray color already slightly lighting the
scene. Delete the default lamp or put it on a different and disabled layer to
see that the spheroid in the scene is dark but still visible in the rendered
3D viewport.
3. It's already possible to change this gray color to some other color by click-
ing on the Color button right under Use Nodes (color at the horizon). This
brings up the same color wheel we have seen for the shader colors. Set
the color to R 0.179 , G 0.152 , and B 0.047 and save the file as
start_05.blend .
Note that both the intensity as well as the general color graduation of the World are
driven by this color. To have more light, just move the Value slider (the vertical one)
towards a whiter hue. To give a general color mood to the scene, pick a color inside
the wheel. This will affect all of the scene's illumination but will show mainly in the
shadows, as shown in the following screenshot: