C++ OpenGL Nothing is rendering when attempting supersampling - c++

Question

I'm attempting to have SSAA featured in my scene. Previously, I have setup the entire scene as an FBO, and it works fine (it renders perfectly on my screen). However as soon as I try to apply SSAA to it, the screen is always black, and I'm unsure why. I've followed a tutorial based on iOS but was fairly simple to copy to windows which can be found here
However as I said when trying a similar technique to that it doesnt work. I understand the theory/concept of SSAA but cannot seem to get it to work. Any help I'd really appreciate it as I can't find much material on it (it is mostly on MSAA or other A.A. techniques)
FBO Initialization
void InitSSAAFBO()
{
// Create the on-screen FBO.
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glFramebufferRenderbuffer(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_RENDERBUFFER,
fboColTex);
glGenRenderbuffers(1, &bigColour);
glBindRenderbuffer(GL_RENDERBUFFER, bigColour);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8,
windowWidth * supersamplingLevel, windowHeight * supersamplingLevel);
glGenRenderbuffers(1, &bigDepth);
glBindRenderbuffer(GL_RENDERBUFFER, bigDepth);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24,
windowWidth * supersamplingLevel, windowHeight * supersamplingLevel);
glGenFramebuffers(1, &fboBig);
glBindFramebuffer(GL_FRAMEBUFFER, fboBig);
glFramebufferRenderbuffer(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_RENDERBUFFER,
bigColour);
glFramebufferRenderbuffer(GL_FRAMEBUFFER,
GL_DEPTH_ATTACHMENT,
GL_RENDERBUFFER,
bigDepth);
// Create a texture object and associate it with the big FBO.
glGenTextures(1, &offscreenTexture);
glBindTexture(GL_TEXTURE_2D, offscreenTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, windowWidth * supersamplingLevel, windowHeight * supersamplingLevel, 0,
GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D, offscreenTexture, 0);
GLenum demoFBOStatus = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (demoFBOStatus != GL_FRAMEBUFFER_COMPLETE) {
fboOkay = false;
cout << "Could not successfully create framebuffer object to render texture!" << endl;
}
else {
fboOkay = true;
cout << "FBO successfully created" << endl;
}
// Unbind FBO for now! (Plug main framebuffer back in as rendering destination)
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
Rendering
void display(void) {
//Bind Large FBO
glBindFramebuffer(GL_FRAMEBUFFER, fboBig);
glBindRenderbuffer(GL_RENDERBUFFER, bigColour);
glClearColor(1.0, 1.0, 1.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, windowWidth * supersamplingLevel, windowHeight * supersamplingLevel);
glEnable(GL_DEPTH_TEST);
DrawScene();
//Bind small/Onscreen FBO
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glBindRenderbuffer(GL_RENDERBUFFER, fboColTex);
glViewport(0, 0, windowWidth, windowHeight);
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glDisable(GL_DEPTH_TEST);
glUseProgram(fboShader);
glBindVertexArray(quadVAO);
glBindTexture(GL_TEXTURE_2D, offscreenTexture);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindVertexArray(0);
glutSwapBuffers();
}
fboShader (Vertex Shader)
#version 330 core
layout (location = 0) in vec2 position;
layout (location = 1) in vec2 texCoords;
out vec2 TexCoords;
void main()
{
gl_Position = vec4(position.x, position.y, 0.0f, 1.0f);
TexCoords = texCoords;
}
fboShader (Fragment Shader)
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D screenTexture;
void main()
{
color = texture(screenTexture, TexCoords);
}