Before we get rolling there is one point which must be addressed. In certain scenarios the term LUT refers to “lookup table” but in others it is referred to as “Lookup Textures”. So the question arises, “which one are we talking about?”, We are talking about the “Lookup textures” which play a dominant roll in AR and VR. Now that we know which version of LUTs we’re talking about we can actually define it. Color LUTs are tables of RGB values. The main tool we use is Spark AR, and in Spark AR you can use said LUTs to quickly create color graded effects for entire scenes. There are two ways to access color LUTs in Spark AR. Option one is to download them from the Spark AR library, while option two is to import your custom made LUT png file to spark AR. So now you can use them, great; but how do they work? We’ll I’m glad you hypothetically asked that. Color values of a camera texture are mapped to the 3D x, y and z coordinates of a location in the color LUT. This location contains a corresponding output color which is rendered over your chosen scene to produce a color effect. There’s a lot of technical jargon being used but rest assured LUTs are a lot more simple then you may have initially imagined. The Odds are pretty high that you’ve encountered the practical application of LUTs before. If you’ve ever used a color filter on an image in Instagram , Snapchat or assorted Adobe products then you’ve used a LUT before. Say you used a black and white filter on a photo. The varying tones of black and white provided by the LUT png file were then mapped to the points on your provided image based on tone and tint of the objects in the image. Initially the subject of LUTs seems overwhelming and confusing, but it’s not as bad as you think. You don’t need to know the programing that makes LUT application possible, leave that to the programmers. But as long as you know what a LUT does and how to apply them in whatever program you’re using then your golden. When it comes to LUTs, successful practical application is the most important aspect, it will make or break the scene it’s applied to.
https://www.vegascreativesoftware.com/us/video-editing/what-are-and-how-use-luts-in-color-grading/