第一章 圖形系統和模型
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圖形系統(Graphics System)
–圖形系統的主要元素
–幀緩存(Frame
Buffer)保存像素;幀緩存的深度(Depth)或精度(Precision)是表示每個像素所用的比特數
–從幾何實體到幀緩存中像素達到顏色和位置的轉換稱爲光柵化(Rasterization)
–輸入設備:物理輸入設備、邏輯設備 -
虛擬照相機模型(Synthetic-Camera Model)
–投影線(Projector)是對象上一點到透鏡中間的一條線
–投影中心(Center of Projection,COP)是透鏡的中心
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應用程序編程接口(Application Programming Interface,API)
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圖形繪製系統的體系結構
–圖形繪製流水線
–頂點處理模塊的主要功能:執行座標變換和計算每個頂點的顏色值
–裁剪模塊和圖元組裝模塊的主要功能:裁剪和組裝圖元
–光柵化模塊的主要功能:對每個圖元輸出一組片元(Fragment)
–片元處理模塊的主要功能:更新呢幀緩存中的像素
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圖形管線(Graphics Pipeline)
–組成部分:建模(Modeling)管線和渲染(Rendering)管線
–建模管線
A)3D模型座標系(3D Model Coordinates):use modeling transformations to put the parts of your model together and then to place your model in a world space
B)3D 世界座標系(3D World Coordinates):This is a single 3D coordinate system in which all the parts of a scene are placed; The scene is independent of the viewer
C)3D 眼睛座標系(3D Eye Coordinates):A scene becomes an image when there is a viewer and a viewing context; A viewer (or camera) is placed in the world space with a position and orientation
D)2D 眼睛座標系(2D Eye Coordinates):The scene is transformed into this coordinate system by projecting each vertex in the scene to its corresponding point in the plane; Depth information is lost in the view
E)2D 屏幕座標系(2D Screen Coordinates):The 2D eye coordinates
are scaled to fit the screen dimensions–渲染管線