User Guide > Learning > Lighting > Global Illumination > Bounced light

Bounced Light


In real-life, light travels in a straight line until it is either bounced, transmitted, or absorbed by a surface. Traditonally, computer graphics rendering focuses on direct illumination does not take these secondary effects into account. Global Illumination considers both direct and indirect light such as the light bouncing from one surface to another (irradiance) or transmitting through a transparent object (caustics).

Topics covered:
Irradiance
Caustics


Irradiance

Irradiance offers a way of achieving global illumination effects without using photons. This is accomplished using the Final Gathering algorithm which calculates illumination by casting rays from objects in the scene, rather from the lights.

The setup of a irradiance-based illumination model involves the creation of a global illumination shader that is assigned to a light source and a few changes to the render output settings.

How to set up irradiance background illumination - In this lesson, you will learn how to use the background settings on a global illumination light to create a scene's illumination. The background can also be replaced by a High Definition light probe for

How to use irradiance with direct lighting - In this lesson, you will learn how to create global illumination effects using the bounced light generated by various direct light sources.


Caustics

To achieve caustic effects, photon rays are used to create a mapping of the scene that takes into account the reflective and refractive qualities of surfaces such as water or glass. The resulting map is then used to distribute light throughout the scene to achieve the caustic effects.

How to set up caustic rendering - In this lesson, you will use photon maps to generate caustic effects through transparent surfaces.