LUT (Look-Up Table / Lookup Table) is a technical term that is extremely important in rendering and optimizing game graphics (technical art). An ultra-high-speed image conversion technology that performs complex color correction (color grading) calculations for the entire screen at lightning speed by sampling a 2D/3D color conversion table texture (LUT) once on the GPU.
Real-world analogy: Instead of calculating the formula every time to get the answer, put a ``quick reference table (LUT) on your desk with answers for all patterns written in advance, and use it as a cheat sheet to instantly get the answer by pointing with your finger
Using the "original red, green, and blue values" as index coordinates (X, Y), you can directly "absorb (sample)" and overwrite pixel colors from a texture (color cube) palette printed in a grid pattern with beautiful pre-calculated color tones. No matter how complex professional movie tone processing may be, it can be applied with almost zero GPU calculation time.
Figure: An infographic that clearly illustrates the basic processing flow and mechanism of LUT (Look-Up Table / Lookup Table) in Japanese notation
Detailed mechanism and operating principle
The ideal color correction data created by the artist in Photoshop etc. is output and registered as a ``2D color band texture (LUT)'', and instead of having the GPU calculate the formula, it is replaced with a texture reading process that ``When this color comes in, output the color at this position in the atlas.''