Gotta think about the scale here. 4k gaming pushes 8 million pixels, 60 times per second. Those pixels are being calculated from light bouncing off of meshes, e

Gotta think about the scale here. 4k gaming pushes 8 million pixels, 60 times per second. Those pixels are being calculated from light bouncing off of meshes, each formed of 10,000-100,000 triangles. More triangles makes your objects look smoother and rounder. Each triangle also has texture information that dictates its color, as well as some specific properties such as reflectiveness. To achieve highly-realistic video games (and CGI), you simply have to have that level of complexity. Even then, the way light is calculated in video games is not realistic at all, it is done that way for significant performance/efficiency gains. Ray tracing is now being added, which is how light behaves in the real world, but that cranks the computational complexity through the roof. That's why it takes thousands of CPU cores 25 hours to render one single frame for a Pixar movie, they go for realistic physics/light.