GLSL 的产生，可以为了更灵活的3D图像编程

APP和GPU的关系图

GLSL 包括　Vertex programs 和 Fragment pgrograms, 实际是对　Geometry 和 Rasterization 的输出

管线处理如下，以前管线不能编程，现在GLSL让管线更灵活了。

Shader 的知识总结：

Shader: a small program for GPU ( like c language, 由 CPU 负责变异，GPU 负责运行，可以使用llvm技术)
Vertex Processor ( handle Vertex shader,  Vertex shader 是一个 main() 程序，作用在每一个Vertex上，控制量的输出：gl_Position）
Fragment Processor ( handle Fragment shader，也是一main  程序，作用在???上(待了解），　gl_FragColor)
其它：shader Log and Cleanup 

communication openGL -> GLSL
Uniform variables:  set by primitive  ( example see : http://www.clockworkcoders.com/oglsl/tutorial2.htm )
Attribute Variables: set inside glBegin/glEnd  () 

Simple:  float, bool, int
vec{2,3,4} a vector of 2,3,or 4 floats
bvec{2,3,4} bool vector
ivec{2,3,4} vector of integers
 matrices 2×2, 3×3 and 4×4 
The data types for texture sampling are:


sampler1D – for 1D textures
sampler2D – for 2D textures
sampler3D – for 3D textures
samplerCube – for cube map textures
sampler1DShadow – for shadow maps
sampler2DShadow – for shadow maps 
Variable Qualifiers
const/attribute/uniform/varying  
 
arrays and structs as C
Control Flow Statements  as C
Functions 
The parameters of a function have the following qualifiers available:


in – for input parameters
out – for outputs of the function. The return statement is also an option for sending the result of a function.
inout – for parameters that are both input and output of a function
Varying Variables
varying float intensity;
A varying variable must be written on a vertex shader, where we compute the value of the variable for each vertex. 

( varying example see : http://www.clockworkcoders.com/oglsl/tutorial4.htm)

http://www.clockworkcoders.com/oglsl/tutorials.html

http://www.opengl.org/documentation/glsl/

笔记：了解GLSL (OpenGL Shading Language)