A raycaster engine is a simple 3D engine that just draws lines from the player’s position to the nearest terrain wall for each horizontal pixel on the screen. It was what was used in one of the foundational 3D action games, id Software’s Wolfenstein 3D.
For those with a coding bent (the word bent seems so suitable when it comes to people who enjoy programming), Youtube account 3D sage demonstrates how to implement a raycaster in a series of three videos. The first one is embedded below:
Later he did another series on implementing the kind of engine that’s in DOOM, but we’ll look at that at a later date.