It samples the gbuffers and checks them for various pbr issues such as:
- BaseColor too bright or too dark
- Metal materials with a very low reflectance (base color too dark)
- Grey metal values
- 100% rough or shiny materials
It then colorizes the view to highlight these areas via a post process. Clicking on any problem areas will automatically open that material or instance for edit. The tooltips of the highlighted areas tell the user how it must be adjusted. The “rules” which the samples compare against can also be changed if you like, but the defaults are based on generally agreed PBR limits.
You can read about the why you should do this in the PBR Check documentation here.
TLDR:
- Metallics set up wrong won’t look correct
- Non-metal values too dark/light hurt scene balance and have poor material response
- 100% rough or shiny could be a mistake - helps you find it.
There is also a reference panel on the left of reference base color values. These can be directly color picked or used as a starting point. There are common materials from charcoal to snow, skin values and measured metals such as iron and chrome etc. It looks like this.
The whole thing is wrapped in a blueprint scriptable tool to make it quick to use with various keyboard shortcuts. That way you can quickly analyze your scene and make any fixes needed.
Hope this answers your question.