A snippet is a piece of GLSL code that can be injected into an another GLSL code. It provides the necessary machinery to take care of name collisions, external variables and snippet composition (call, +, -, /, *).
A snippet can declare uniforms, const, attributes and varying using random names. However, these names will be later mangled such as to avoid name collisions with other snippets and/or main code. This means that any snippet variable must be accessed through the snippet (snippet["variable"]) to be able to change its value within the main program.
Let's consider a simple piece of code:
uniform float alpha;
vec4 process(vec3 color)
{
return vec4(0,0,0,alpha);
}Not very interesting code but it will serve our purpose. To create a snippet