Raycasting is an old way of drawing 3D scenes, which was used by pseudo-3D games on older computers. Like this:
Back then, the game drew the world by casting one ray per vertical line of the screen, to find out how far it was to the nearest wall, which were aligned to a grid in the case of Wolf3D in order to make it fast enough. Then it drew a scaled vertical segment of the appropriate texture, which could be done fast because no divisions needed to be done per pixel to adjust for perspective, because all pixels in that vertical segment were the same distance from the camera.
Nowadays, computers are fast enough that you don't have to reprent the level with a grid or a 2D map of line segments. You can use polygons. And you can cast one ray per pixel on the screen.
But nowadays 3D cards can draw a polygon much faster than it could be calculated by the CPU, so you might be limited in the resolution, and unless you support mipmaps you're gonna see a lot of aliasing.
Back then, the game drew the world by casting one ray per vertical line of the screen, to find out how far it was to the nearest wall, which were aligned to a grid in the case of Wolf3D in order to make it fast enough. Then it drew a scaled vertical segment of the appropriate texture, which could be done fast because no divisions needed to be done per pixel to adjust for perspective, because all pixels in that vertical segment were the same distance from the camera.
Nowadays, computers are fast enough that you don't have to reprent the level with a grid or a 2D map of line segments. You can use polygons. And you can cast one ray per pixel on the screen.
But nowadays 3D cards can draw a polygon much faster than it could be calculated by the CPU, so you might be limited in the resolution, and unless you support mipmaps you're gonna see a lot of aliasing.