OpenGL 3.30 / GLSL 3.30 - MRT outputting black textures - c++

Question

I've been stuck with this problem for about four days now. I'm trying to get my geometry to rendered into an FBO (G-buffer) with three textures (albedo, normal, depth). So far, I've 'somewhat' implemented MRT functionality, but when I use gDEBugger to inspect the textures, they just appear black. No matter what I change, they result in solid black. The actual values outputted are correct, I checked by disabling MRT to make the fragment shader output to back buffer. The textures are being initialized properly, gDEBugger properly displays the parameters I have put for them. But they all just have a solid black (0, 0, 0, 255) fill.
There's hardly any elaborate information on MRTs for GLSL 3.30. I've relied entirely on answered questions here, along with the OpenGL/GLSL docs and tutorials across the web (outdated, but I updated the code). I've probably spent a full day looking for a solution for this problem on Google. If there's something wrong with the ordering of the code, or syntax, please point it out. I don't even know if this implementation is correct anymore...
I'm using Visual C++ 2010, OpenGL 3.30 and GLSL 3.30 (as said in the title). For my libraries, GLFW 3.0 is being used for the windows, input, and OpenGL context, and GLEW 1.10.0 for extensions.
Keep in mind that all of this code is taken from my wrapper class. The ordering of the code is how it is all run at runtime (in other words, it's like as if I didn't have a wrapper class, and all of the code was in main ()).
Initialization Stage
// Initialize textures
glGenTextures (3, tex_ids);
glEnable (GL_TEXTURE_2D);
glBindTexture (GL_TEXTURE_2D, tex_ids[0]); // Diffuse
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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_RGB8, res.x, res.y, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
glBindTexture (GL_TEXTURE_2D, tex_ids[1]); // Normal
glTexParameterf (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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_RGB8, res.x, res.y, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
glBindTexture (GL_TEXTURE_2D, tex_ids[2]); // Depth
glTexParameterf (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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_DEPTH_COMPONENT32, res.x, res.y, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glBindTexture (GL_TEXTURE_2D, 0);
glDisable (GL_TEXTURE_2D);
// Initialize FBO
glEnable (GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, tex_ids[0]);
glFramebufferTexture2D ( GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D,
tex_ids[0],
0 ); // diffuse
glBindTexture(GL_TEXTURE_2D, tex_ids[1]);
glFramebufferTexture2D ( GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT1,
GL_TEXTURE_2D,
tex_ids[1],
0 ); // normal
glBindTexture(GL_TEXTURE_2D, tex_ids[2]);
glFramebufferTexture2D ( GL_FRAMEBUFFER,
GL_DEPTH_ATTACHMENT,
GL_TEXTURE_2D,
tex_ids[2], 0 ); // depth
glBindFramebuffer (GL_FRAMEBUFFER, 0);
glDisable (GL_TEXTURE_2D);
// Initialize shaders
// Snipped out irrelevant code relating to getting shader source & compiling shaders
glBindFragDataLocation (renderer_1prog, GL_COLOR_ATTACHMENT0, "diffuse_out");
glBindFragDataLocation (renderer_1prog, GL_COLOR_ATTACHMENT1, "normal_out");
glBindFragDataLocation (renderer_1prog, GL_DEPTH_ATTACHMENT, "depth_out");
// More snipped out code relating to linking programs and finalizing
Draw Stage - called on every frame
// Bind everything
glUseProgram (renderer_1prog);
glBindFramebuffer (GL_DRAW_FRAMEBUFFER, fbo_id);
GLenum targ [3] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_DEPTH_ATTACHMENT };
glDrawBuffers (3, targ);
// Draw mesh
glEnable (GL_CULL_FACE);
glEnable (GL_DEPTH_TEST);
teshmesh.draw ();
// Unbind fbo
glDisable (GL_CULL_FACE);
glDisable (GL_DEPTH_TEST);
glBindFramebuffer (GL_READ_FRAMEBUFFER, 0);
glBindFramebuffer (GL_DRAW_FRAMEBUFFER, 0);
Vertex Shader
#version 330
layout(location = 0)in vec4 v;
layout(location = 1)in vec3 c;
layout(location = 2)in vec3 n;
out vec4 pos;
out vec3 col;
out vec3 nrm;
uniform mat4 projection;
uniform mat4 view;
uniform mat4 world;
void main () {
gl_Position = projection * view * world * v;
pos = view * world * v;
pos.z = -pos.z / 500.0;
col = c.xyz;
nrm = n;
}
Fragment Shader
#version 330
in vec3 col;
in vec3 nrm;
in vec4 pos;
layout(location = 0) out vec3 diffuse_out;
layout(location = 1) out vec3 normal_out;
layout(location = 2) out vec3 depth_out;
out vec3 o;
void main () {
diffuse_out = col;
normal_out = (nrm / 2.0) + 0.5;
depth_out = vec3 (pos.z, pos.z, pos.z);
}

Answer 1

There are a few problems here. Starting with the smallest:
glBindFragDataLocation (renderer_1prog, GL_COLOR_ATTACHMENT0, "diffuse_out");
glBindFragDataLocation (renderer_1prog, GL_COLOR_ATTACHMENT1, "normal_out");
glBindFragDataLocation (renderer_1prog, GL_DEPTH_ATTACHMENT, "depth_out");
These are pointless. You used layout(location) syntax in your shader to specify this, and that takes priority over OpenGL-provided location settings.
Also, these are wrong. You don't put the FBO buffer attachment name into the location; you put an index into the location. So even if you didn't use layout(location), this is simply incorrect. glBindFragDataLocation will emit an OpenGL error, since the location will most assuredly be larger than GL_MAX_DRAW_BUFFERS​.
Considering how many OpenGL errors your code should emit, I'm rather surprised that your use of gDEBugger didn't tell you about any of these.
glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB8, res.x, res.y, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
GL_RGB8 is not one of the required image formats for render targets. Therefore, the implementation is not required to support it; it may but it doesn't have to. And since you never bothered to check the completeness of the FBO (FYI: you should always do that), you didn't test that this combination of formats is valid.
Never render to a 3-component image. Pick 4, 2, or 1 instead.
GLenum targ [3] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_DEPTH_ATTACHMENT };
glDrawBuffers (3, targ);
This is probably your main problem: your glDrawBuffers call fails. glDrawBuffers sets the color buffer outputs. The depth buffer is not a color buffer. There's only one depth buffer, so there's no need to set it.
To write to the depth buffer... well, you shouldn't be writing a user-calculated value to the depth buffer. Just let the regular depth buffer writing handle it. But if you want to (and let me remind you again, you do not), you write to gl_FragDepth. That's what it's for.