The Global Illumination Maps

The global illumination maps are used to model the light falling on an object from the environment

As mentioned in the Introduction to Vulkan: Migrating from OpenGL ES, image-based lighting attempts to simulate global illumination. In global illumination, every point of the environment contributes as a light source, not just the explicit light sources like the Sun. Calculating incoming light for each point in a scene for each pixel on the screen is impractical. Thankfully, this calculation can be trivially pre-computed for the environment map.

Two maps are produced from the environment map: an irradiance map and a pre-filtered reflection map. The irradiance map models the diffuse light falling on a surface, whereas the prefiltered reflection map models how light will be reflected off a surface based on the BRDF.

This section will explain how these maps were created and how they are used in this demo.