Page History
...
Render Region Division
...
The parameters in this panel adjust V-Ray's rendering regions (sometimes referred to as buckets), when the Image Sampler Type is set to Bucket. A bucket is a rectangular (usually square) section of the currently rendered frame that is rendered independently from other sections. Buckets are used when V-Ray uses a non-progressive image sampler. For more information please see the Render Region Division page.
...