Raycastlib (RCL) is a [public domain](public_domain.md) ([CC0](cc0.md)) [LRS](lrs.md) [C](c.md) [library](library.md) for advanced 2D [raycasting](raycasting.md), i.e. ["2.5D/pseudo3D"](pseudo3d.md) [rendering](3d_rendering.md). It was made by [drummyfish](drummyfish.md), initially as an experiment for [Pokitto](pokitto.md) -- later he utilized the library in his game [Anarch](anarch.md). It is in spirit similar to his other LRS libraries such as [small3dlib](small3dlib.md) and [tinyphysicsengine](tinyphysicsengine.md); just as those raycastlib is [kept extremely simple](KISS.md), it is written in pure C99, with zero [dependencies](dependency.md) (not even [standard library](stdlib.md)), it's written as a single file single header library, using no [floating point](float.md) and tested to run interactively even on very weak devices (simplified version was made run on [Arduboy](arduboy.md) with some 2 KiB of RAM). Two rendering [algorithms](algorithm.md) are provided to choose from: simple (only same height floor and ceiling, allowing textured floor and ceiling) and complex (allowing variable floor and ceiling, without textured floors and ceilings). Per rendered frame both algorithms always draw every screen pixels exactly once, without any overdraw and holes, which is very advantageous and elegant; the simple algorithm additionally also guarantees the pixels to be drawn in exact same linear order every time. It is very flexible thanks to use of [callbacks](callback.md) for communication, allowing e.g. programming arbitrary "[shader](shader.md)" code to implement all kinds of effects the user desires or using [procedurally generated](procgen.md) environments without having to store any data. The library implements advanced features such as floor and ceiling with different heights, textured floor, opening door, simple [collision detection](collision_detection.md) etc. It is written in just a bit over 2000 [lines of code](loc.md).
The repository is available at https://git.coom.tech/drummyfish/raycastlib. The project got 45 stars on gitlab before being banned for author's political opinions.
