Figure 6.27 - Irradiance Volume in the scene
The Irradiance Volume has a box-like shape, and it identifies an area
where Eevee will later process indirect light bounces. Only what is inside
the Probe volume receives indirect light bounces. You can add as many
of those Probes as you need.
The next probe we will need is a Reflection Cubemap that captures
reflections and cast them in glossy surfaces. Press SHIFT+A again and
from the Light Probes group, add a Reflection Cubemap. Using the G
key, raise the probe from the ground level and place it in your scene's
middle.
Unlike an Irradiance Volume with a box-like shape, a Reflection
Cubemap has a default shape of a sphere. Use a scale transformation to
increase your probe's size until it becomes bigger than your scene
(Figure 6.28).