Rasterisaation

Rasterization is a fundamental process in computer graphics used to convert vector graphics into a raster image, which is a grid of pixels. This process is essential for displaying images on screens, as monitors are inherently pixel-based. When a 3D model or 2D vector shape is to be displayed, its geometric data, typically represented by vertices and edges, is transformed and projected onto a 2D plane. Rasterization then determines which pixels on the screen grid fall within the boundaries of these projected shapes.

The core of rasterization involves algorithms that efficiently calculate pixel coverage. For lines, algorithms like Bresenham's line algorithm are used to determine which discrete pixels best approximate the line's path. For polygons, scanline rasterization or fragment shaders are employed. Scanline approaches process the image row by row, identifying the segments of the polygon that intersect each scanline and filling the pixels within those segments. Fragment shaders operate at a finer level, determining the color of individual pixels or fragments based on interpolation of vertex attributes like color or texture coordinates.

The output of rasterization is a bitmap or raster image, where each pixel has a specific color value. This process is computationally intensive, especially for complex scenes with many polygons and high-resolution displays. Graphics processing units (GPUs) are specialized hardware designed to perform rasterization and other graphics operations very quickly, enabling real-time rendering of interactive 3D environments.