Includes are special core shaders that contain shared code between different shaders, which all use the .glsl file extension This page will document them and their uses.
Contains three functions:
linear_fog(): Tints a pixel based on its passed-in vertexDistance value.
linear_fog_fade(): Passes out how faded a pixel should be, using similar logic to linear_fog().
cylindrical_distance(): Used after 1.18.1 to calculate vertexDistance rather than a simple length function, giving fog a cylindrical shape.
Contains two functions:
minecraft_mix_light(): Controls the light of entities and items in the inventory. Does not seem to use any lightmap data, in favor of doing a similar calculation to minecraft_sample_lightmap() in the entity shader itself.
minecraft_sample_lightmap(): Controls the light of blocks. Two values are passed in, the lightMap and the uv. lightMap is a sampler2D that holds all of the color data of the lightmap, and uv contains the light level. The x value of uv is the block light times 16, and the y value is the sky light times 16. GUI elements such as text or items in the inventory, when altered to use the function, seem to use both a block and sky light of 15.
Contains one function: mat2_rotate_z(), which creates a 2d rotation matrix.
Contains one function: projection_from_position(), which projects an image from a position. Used in the vertex shader for the end portal image.