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Programming Linux Games phần 3

Tham khảo tài liệu 'programming linux games phần 3', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 70 CHAPTER 4 Computer Graphics Hardware Every personal computer is equipped with a video controller of some sort. This set of chips is responsible for producing images on the screen based on the data contained in a certain area of memory the framebuffer . In addition to this basic drudgery the video controller often assists software by providing hardware-accelerated drawing functions. Video controllers usually reside on replaceable video cards that can be easily upgraded as video technology progresses. Video cards contain a unit called a CRTC an acronym for cathode ray tube controller. This device either a separate chip or part of another chip instructs the monitor to redraw its picture at regular intervals. The image on a computer screen is composed of horizontal lines on a fluorescent surface and the monitor s hardware updates these from top to bottom. Each completed image is called a refresh. The CRTC instructs the monitor to perform a new refresh at least 60 times each second. The brief pause between refreshes is known as the vertical retrace because this is when the monitor s electron beam returns to the top of the screen. No matter how quickly the data in the framebuffer changes the monitor is not updated until the next refresh. The video hardware s refresh rate is therefore of great interest to a game developer. The image on a computer screen is divided into discrete colored areas called pixels short for pictorial elements . Each pixel can be individually controlled by the video card. The resolution of a display specifies the number of pixels across and down for instance a screen with a resolution of 640 by 480 is a matrix of 640 columns and 480 rows. The video card uses a device called a RAMDAC random access memory digital-analog converter to pump these individual pixels from the framebuffer memory to the monitor. Video card manufacturers like to brag about the speed of their RAMDAC components. Since there are a lot of pixels on the screen anywhere from 64