Integrator

The integrator is the rendering algorithm used for lighting computations. Cycles currently supports a path tracing integrator with direct light sampling. It works well for various lighting setups, but is not as suitable for caustics and some other complex lighting situations. Rays are traced from the camera into the scene, bouncing around until they find a light source such as a lamp, an object emitting light, or the world background. To find lamps and surfaces emitting light, both indirect light sampling (letting the ray follow the surface BSDF) and direct light sampling (picking a light source and tracing a ray towards it) are used.^[34]
There are two types of integrators:

1. The default path tracing integrator is a pure path tracer. At each hit it bounces light in one direction and picks one light to receive lighting from. This makes each individual sample faster to compute, but typically requires more samples to clean up the noise.
2. The alternative is a branched path tracing integrator which at the first hit splits the path for different surface components and takes all lights into account for shading instead of just one. This makes each sample slower, but reduces noise, especially in scenes dominated by direct or one-bounce lighting.