In the real world, all objects are lit by a combination of direct light (photons that travel directly from a light source to illuminate an object) and indirect light (photons that travel from the light source, hit one object and bounce off of it and then hit a second object, thus indirectly illuminating that object). “Global illumination” (GI) is a term for lighting systems that model this effect. Without indirect lighting, scenes can look harsh and artificial. However, while light received directly is fairly simple to compute, indirect lighting computations are highly complex and computationally heavy.