Complex light sources consist of several emitting surfaces. They are generated like geometric objects of type 'complex object' (see below). All subsurfaces must be embedded in the same material but are completely free to be positioned and oriented in space. The amount of rays started at the individual surfaces is computed according to the relative surface area of each particular surface with respect to the total area of the light source.

In the object's dialog, use the Geometry button to open a subwindow which allows the definition of the subobjects exactly the same way as described for complex objects:

The Objects button opens the list of the individual surfaces - here its a large collection of triangles obtained from a CAD program:

Here is the example of an emitting bended fiber: