The render graph system is a set of APIs you use to write a Scriptable Render Pass in the Universal Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
See in Glossary (URP).
When you use the render graph API to create a Scriptable Render Pass, you tell URP the following:
You can then add your Scriptable Render Pass to the URP renderer. Your Scriptable Render Pass becomes part of URP’s internal render graph, which is the sequence of render passes URP steps through each frame. URP automatically optimizes your render pass and the render graph to minimize the number of render passes, and the memory and bandwidth the render passes use.
URP does the following to optimize rendering in the render graph:
On mobile platforms that use tile-based deferred rendering (TBDR), URP can also merge multiple render passes into a single native render pass. A native render pass keeps textures in tile memory, rather than copying textures from the GPU to the CPU. As a result, URP uses less memory bandwidth and rendering time.
To check how URP optimizes rendering in your custom render passes, refer to Analyze a render graph.