This class can be simply injected into an existing OpenGL code to apply some post processing effects on the rendered result. Simply include the hehpp file and create an instance of GLInjection class. Then init the object somewhere where the scene is initialized so that the init function is called only once. Add the call to render function right before the swapping of the buffers or other kind of frame buffer presentation mechanism. For example, right before the call of glfwSwapBuffers or SDL_GL_SwapWindow. Edit the fragment shader to adjust the effects. An example with LearnOpenGL tutorial is placing the init here and render here.