User Guide > Lighting   

Global Illumination

In real-life, light travels in a straight line until it is either bounced, transmitted, or absorbed by a surface. Global illumination lets you achieve a higher degree of photorealism by calculating the bouncing and transmission of light. Global Illumination solutions can deal with light bouncing from one surface to another (irradiance), which is often revealed by the bleeding of colour from one surface to another, and light transmitting through a transparent object (caustics).

Topics covered:
Irradiance
Caustics


Irradiance

Irradiance offers a way of achieving global illumination effects using the Final Gathering algorithm which calculates illumination by casting rays from objects in the scene, rather than from the lights.

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

Environment Illumination - Environment illumination can be achieved using the GI shader's background color to define a scene's lighting. This technique can be enhanced using image-based lighting where a high definition light probe image can be applied as an environment.

Bounced Light - In this lesson, you will learn how to create global illumination effects using the bounced light generated by various direct light sources. The bouncing of this direct light into the dark areas of a scene provides a more realistic ambient look and creates the colour bleeding effect that is often associated with Global Illumination.

Incadesence - Objects with constant shading that simulates incadesence can also be used as sources of light in a global illumination rendering.


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.

Caustic Light Effects - In this lesson, you will use photon maps to generate caustic effects through transparent surfaces.