Raycast Corridor 3D

Level is a two-dimensional grid of solid or empty cells. For each vertical column of pixels the renderer casts a ray until it strikes a wall, uses the distance to decide how tall that column should be, and samples a texture to fill it. Floors and ceilings are flat colours or simple planes, everything else is a scaled sprite, and walls share one height with no rooms above rooms.

id Software shipped Wolfenstein 3D in 1992 on PC hardware with no graphics acceleration, where general 3D rendering was hopeless but a tightly constrained special case was not. Restricting the world to a grid removed almost all of the mathematics, and the studio had rehearsed the approach in earlier titles including Catacomb 3-D. Distribution mattered as much as the renderer, since shareware put a fast first-person game on machines bought for spreadsheets.

Speed was the whole argument. A first-person view running at a responsive frame rate turned the viewpoint from a curiosity into an action genre, and it set expectations for movement, weapons and level flow that persist. Grid geometry also limited what those levels could say, because a world of right angles and equal heights cannot describe a real place. Every later renderer was an attempt to lift that restriction.