desaturation_shader_vs.glsl

#version 330 core
layout ( location = 0 ) in vec2 vertex_position;
layout ( location = 2 ) in vec2 vertex_uv;
uniform mat4 M_mvp;
out vec2 uv;
void main()
{
  gl_Position = M_mvp * vec4( vertex_position , 0.0 , 1.0 );
  uv = vertex_uv;
}