http://blog.csdn.net/luckheadline
1.渲染的目標
將計算機模型轉化爲圖像，可能是也可能不是具有真實感的圖片。
2.交互式渲染
快速但是質量有限，大體上遵循一定的操作模式(渲染流水線)
3.離線渲染
ray tracing; global illumination
4.渲染需要執行的任務(無特別順序)
(1)將所有的三維幾何圖形投影到圖像平面
幾何變換
(2)確定哪些元素可見
hidden surface removal
(3)確定一個幾何圖形會覆蓋哪些像素
scan conversion
(4)計算可見表面的每個點的顏色
光照，投影，紋理映射
5.渲染流水線
渲染流水線是將幾何模型轉化爲數字圖像的操作序列的抽象模型，是圖形硬件工作方式的抽象。實際中，各種渲染流水線的實現細節是不同的。
Geometry Database-->Model/View transform-->Lighting-->Perspective Transform-->Clipping-->Scan Conversion-->Texturing-->Depth Test-->Blending-->Frame-buffer
6.Geometry Database
application-specific data structure for holding geometric information; depends on specific needs of application
7.Model/View Transform
model transformation: map all geometric objects from local coordinate system into world coordinates
viewing transformation: map all geometry from world coordinates into camera coordinates
8.Lighting
compute brightness based on property of material and light position(s); computation is performed per-vertex
9.Perspective Transformation
projecting the geometry onto the image plane;
projective transformations and model/view transformations can all be expressed with 4x4 matrix operations
10.Clipping
removal of parts of the geometry that fall outside the visible screen or window region; may require re-tessellation of geometry
11.Scan Conversion
turn 2D drawing primitives into individual pixels (discretizing/sampling);interpolate color across primitive;generate discrete fragments
12.Texture Mapping
"gluing images onto geometry"; color of every fragment is altered by looking up a new color value from an image
13.Depth Test
remove parts of geometry hidden behind other geometric objects;perform on every individual fragment
14.Blending
combine new & old values with arithmetic operations; draw from farthest to nearest
15.framebuffer
video memory on graphics board that holds image; double-buffering
16.Pipleline Advantages
modularity
easy to parallelize
only local knowledge of the scene is necessary
17.Pipeline disadvantages
limited flexibility
some algorithms would require different ordering of pipeline stages
only local knowledge of scene is available