 Cycles currently supports a path tracing integrator with "direct light sampling".It works well for a variety of lighting setups, but it is not as suitable for caustics and certain other complex lighting situations.Rays are traced from the camera into the scene, bouncing around until they find a light source (a lamp, an object material emitting light, or the world background), or until they are simply terminated based on the number of "maximum bounces" determined in the light path settings for the renderer.