The Global Illumination (GI) Render Element is a color image that stores indirect lighting information coming from reflected diffuse light in a scene (without direct light and reflection contributions) when Global Illumination is enabled in Render Settings. This element may be used directly in Back to Beauty compositing and adjusted for brightness and color to control the final image easily.

For even more control of indirect illumination without re-rendering the scene, the Global Illumination render element may be re-assembled by multiplying the GI Raw Render Element by the Diffuse Render Element:

GI Raw x Diffuse = GI