Overview of Materials in Cycles - Blender 2.6 Cycles: Materials and Textures - page 27

Creating a mesh-light material
In this recipe, we will see how to create a mesh-light material to be assigned to any
mesh object and used as source light to light the scene.
Getting ready
Until now we have used the default lamp (a Point light) already present in the scene
for lighting the scene. By enabling the node system for the lamp, we have seen that
the lamp uses a material created by connecting an Emission node to the Lamp Out-
put node.
The good news is that, exactly because it's a node material, we can assign an Emis-
sion shader also to a mesh. For example, to a plane conveniently located, scaled,
and rotated to point to the scene. Such a light emitting mesh is called a Mesh-light .
Being a mesh, the Emission shader node output must be connected to the Surface
input socket of a Material Output node instead of the Lamp Output node.
The light emission, coming from a surface and not from a point, is a lot more diffuse
and softer than a lamp. A mesh-light can be any mesh of any shape and, therefore,
can be easily used as an object taking part in the scene and being, at the same time,
the real light source of the rendering—for example, a table lamp, or a neon sign, or
a television screen. As a pure light-emitting plane, it's usually used as a sort of pho-
tographic diffuser. Two or three mesh-lights strategically placed can realistically simu-
late a photo studio situation.
1. Starting from the start_07.blend file, click on the eye lamp icon in the
Outliner to enable it again.
2. Right-click the lamp in the 3D view and press Shift + S to bring up the
Snap menu. Left-click on the Cursor to Selected item.
3. Press Shift + A with the mouse pointer in the 3D view and add a plane to
the scene at the cursor's location.
4. Come out of edit mode (press Tab ). Shift select the lamp; now you have
both the just added plane and the lamp selected, and the latter is the active
one.
5. Press Crtl + C to bring up the Copy Attributes menu and select the Copy
Rotation item.
6. Rename this plane to Emitter .