| OCR Text |
Show CHAPTER TWO A GENERAL ALGORITHM FOR DISPLAYING CURVED PATCHES An algorithm for establishing a correspondence between points on a patch and raster elements is described in this chapter. It applies to patches and surface sections in general, hence the algorithm presented will not be specific at the outset. Later on, when a specific kind of patch is used, more detail will be given. Before presenting that algorithm, however, some terms must be defined. DEFINITIONS A "raster-scan device" or "raster-display" is the device that we will consider for final output of an image. The rectangular array of "dots" that is produced on a raster-display is called the "raster." Each dot will usually be called a "raster-element." The raster element covers a very small area of the raster; however, It should not be thought of as a point. A row of raster-elements is a "scan-line." Scan-lines are usually produced in sequential order, termed "scan-line-order." Each raster-element has a brightness that is determined by the intensity value for that raster-element. The process of taking the intensity values and putting the dots on the raster with the corresponding intensities is called "displaying." |
