Table of Contents
Introduction
Raycasting is a rendering technique to create a 3D perspective from a 2D map. [1] The main advantage of this technique is to be fast and affordable in real time for the PCs of the early 90's. This technique is also called 2.5D to differentiate it from the first true 3D engine such as the Quake engine (aka ID Tech 1), but 2.5D can also reference other rendering technique not discussed here, such as axonometric projections like the isometric projection.
Raycasting must not be confused with raytracing. Raytracing is another rendering technique which is much heavier and slower in term of computation. Raytracing computes the path of each ray of light of a given source to determine the lightning of the scene. However, since 2019, the power of the newest graphical processing units tends to offer raytracing in real time.
Finally, if raycasting is really fast for the screen resolution of the early 90's, such as 320x200, 640x400 or 640x480, its performances are very bad for higher, modern resolution. The 3D computing API such as OpenGL, Vulkan or DirectX must rather be used for that.
Historical information
The game which put this techique at the center stage was id Software smash hit Wolfenstein 3D.
Technical information
Build:
Sloped ceilings and floors
High-res SVGA and VESA support
True rooms above rooms
Moving vehicles
Transparent sprites
Underwater swimming
Map sectors can move during game play
References
[1] : Lode's Computer Graphics Tutorial