How intensities of pixels on a image are calculated in EU4 ?

I would like to see how intensities of pixels, which are “pixel 1” and “pixel 2” in Fig.1 on a URL shown below, are calculated in EU4.

Please tell me the document, book or URL, which explain that in detail.

Thank you.

Google Photos

This is a big topic known as Physically Based Rendering or PBR for short.

The short answer is that most of the intensity values are determined via the Diffuse albedo and Specular calculations for the scene which for simple materials are Lambert and GGX respectively. There are lots of good reading materials on the subject but if you want to know exactly how the final values are calculated you will have a long road ahead of you. If you research those first two methods of lambert and ggx you will be on your way though.

And if you are after more of an “ELI5” reddit answer: