Rasterization

Rasterisation (or rasterization) is the task of taking an image described in a vector graphics format (shapes) and converting it into a raster image ( A series of pixels, dots or lines that when they come together on a display, they recreate the image). The rasterised image may then be displayed on a computer display, video display or printer, or stored in a bitmap file format. Rasterisation may refer to either the conversion of models into raster files, or the conversion of 2D rendering primitives such as polygons or line segments into a rasterized format. The latter is used to convert the polygonal 3D vector world created for Catacomb 3D and present it as a 2D display that matched with the raster sprites used for game objects.

This approach was later replaced by raycasting, in the engine's successor used in Wolfenstein 3D. Compared with other rendering techniques such as ray tracing, rasterisation is extremely fast. However, rasterization is simply the process of computing the mapping from scene geometry to pixels and does not prescribe a particular way to compute the color of those pixels. Shading, including programmable shading, may be based on physical light transport, or artistic intent.

The process of rasterising 3D models onto a 2D plane for display on a computer screen ("screen space") is often carried out by fixed function hardware within the graphics pipeline. This is because there is no motivation for modifying the techniques for rasterisation used at render time[clarification needed] and a special-purpose system allows for high efficiency.