The GPU Usage Area

The GPU Usage Area is similar to the CPU Usage Area, except that it shows method calls and processing time as it occurs on the GPU. Relevant Unity method calls in this Area will relate to cameras, drawing, opaque and transparent geometry, lighting and shadows, and so on.

The GPU Usage Area offers hierarchical information similar to the CPU Usage Area and estimates time spent calling into various rendering functions such as  Camera.Render() (provided rendering actually occurs during the frame currently selected in the Timeline View).

The GPU Usage Area will be a useful tool to refer to when you go through Chapter 6, Dynamic Graphics.