View Indirect Illumination
Indirect Illumination is effectively the illumination within a scene that does not come from an actual light source, and effectively refers to reflected light. In general terms, indirect illumination is interchangeable with global illumination when discussing computer imaging. As a feature, though, that is not the case within the Cinema 4D application in terms of a feature. (The discrepancy arises from the iterative nature of computer graphics science and software application development.)
Indirect illumination is a sampling method to resolve bounce lighting employed within the physically accurate rendering engine that debuted in Release 13. Unlike other sampling methods, such as QMC, indirect illumination uses no tricks or special optimizations to produce results and is thus referred to as a “brute force” sampling method. To further isolate the feature, indirect illumination is not available when other global illumination methods are chosen from the Effects menu in the physical renderer.
So what does indirect illumination do? Like other methods within Cinema 4D, indirect illumination determines how much illumination energy is passed on to objects and surfaces as that energy emanates from a light source of some kind, and travels through the scene. You can almost consider virtually any polygonal face within the scene as a lightsource, as that is a simplistic view of how indirect illumination actually works. In short, it allows for a realistic bounce light effect, where a surface reflecting light can add to the ligthing perceived upon another surface, including the color of the bounced light as it mixes with the color of the surfaces that it had previously visited.
Indirect illumination can be fined tuned to a great extent via the its diffuse depth and sampling settings within the physical render settings panel, in the basic properties section. For a detailed exploration of the various settings, how they operate, and how best to use them, please refer to the excellent series of tutorials on the physical renderer by Patrick Goski, located here (insert final link).