The Brute force method for computing global illumination recomputes the GI values for every single shaded point separately and independently from other points. This method is very accurate, especially if you have many small details in the scene. For more information on how Brute Force works, see the Brute Force GI topic in the Reference section.
To speed up calculations with Brute Force as the Primary Rays engine, you can use the Light Cache engine for calculating Secondary Rays.
This rollout is available only if Brute Force has been chosen as either the Primary Rays or Secondary Rays GI engine in the Global Illumination Settings.
UI Path: ||V-Ray Asset Editor|| > Settings > Global Illumination > Brute Force
(When Brute Force is set as the Primary or Secondary Rays engine.)
GI Depth – Specifies the number of light bounces that will be computed. GI Depth will also be used to calculate Interactive rendering GI Depth. For more information, see the Light Bounces example on the Global Illumination Settings page.