Book of shaders notes

.hello

Getting started 
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GLSL stands for openGL Shading Language

- Each pipe of thread has to be independant of each other

- Threads are blind to what each other is doing

- DATA MUST FLOW IN THE SAME DIRECTION

- impossible to check the result of another thread, modify input data, or pass outcome of one thread to another

- Each thread is blind and memoryless 




Hello world 
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- Shader language has a single `main` functino that returns a color at the end

- Final pixel colour is assigned to `gl_FragColor`

- vec4 = stands for four dimentional vector of floating point precision

- RED, GREEN, BLUE, ALPHA

RBG ALPHA
RGBA 

same as css order

always use 1.0 whole decimals for floats or some browsers will break


Can specify precisions:

	precision mediump float;

precision lowp float; or precision highp float;




Uniforms 
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ALL THREADS ARE BLIND TO EACH OTHER

- We need to be able to send message from the CPU to all threads
- each thread receives the same data (UNIFORM) which it can _read only_ 

INPUTS ARE CALLED UNIFORM :: 
-  supported types: float, vec2, vec3, vec4, mat2, mat3, mat4, sampler2D and samplerCube

- Uniforms are little bridges /-------\ between the CPU and GPU 

-