2.1. LUTs
An LUT is a specific kind of sprite that the game uses to create multiple color palettes for a sprite from the same image. They are most often used for cosmetics, animal variants, and UI elements.
LUT stands for "look-up table". They are an optimization used by many different games to manipulate colors and how assets display, similar to shaders. In Fields of Mistria, most LUTs are 256 pixels tall, and at least 2 pixels wide. Mistria's LUTs work by organizing palettes by their RGB red value, which is why there are 256 rows.
In general, the LUT file defines the color variants its associated sprite can have, with the width of the file defining the number of color variations of the sprite.
As an example, let's take a look at the LUT used for player skin tone.
The first column of the image (which we can think of as a table of sorts) matches the colors of the sprite image itself. The proceeding columns then define the color variants of the sprite when it displays in-game. So, to use the current example, when the game sees that bright magenta color, it will replace it with one of the colors to the right in that row depending on which color variation has been chosen by the user.
Now let's take a look at the whole LUT, which has been condensed so you can see the relevant information:
Each of the different colors on the base sprite image have exactly one row assigned to them on the LUT. This is done according to their R value. This is why if you have ever edited a sprite that uses an LUT and used two colors that are very similar to each other, they end up being replaced by the same color after the LUT is applied, because the two colors you chose have the same R value.
If you want to edit a certain color variant of a sprite that uses an LUT, simply edit the colors in the relevant column.
If you are creating a new sprite using an existing LUT (such as a hair cosmetic styled similarly to the vanilla hair cosmetics), simply use the existing colors in the leftmost column of the LUT to create your sprite. In these cases, it's helpful to reference existing similar sprites.
Due to the constraints already outlined above, creating new LUTs from scratch would mean counting pixels for the R value of every color you use in your base sprite. However, thankfully, we don't actually have to do that! Felix (a.k.a D3Ulo), fellow MOMI contributor and modding community member, created a tool for creating, editing, and viewing LUTs easily. The tool is extremely helpful for troubleshooting and editing without having to install mods and load the game directly.
If any sprites in your game show up as entirely black, it is most likely an LUT issue. We recommend double checking that all files are loading correctly and using Felix's LUT editor tool (linked above) to check that the LUTs are being applied how you intend them to.