OpenGL: Depth Attachment breaks Framebuffer

Question

I need a fresh pair of eyes. While working on rewriting my engine, I stumbled upon this issue while writing the Deferred Rendering path. The framebuffer displays only if I don't use a depth attachment, which means that the rendering is faulty, but if I do, all the outputs are blank. I wrote a lot of graphics handling classes but I broke down the code here:

Initialization:

glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
glClearColor(0, 0, 0, 1);
glViewport(0, 0, 1024, 768);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
ShaderPreparation();

numBuffer = 3;
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
numBuffers = numBuffer;
targetBuffer = 0;
textures = new unsigned int[numBuffers];
glGenTextures(numBuffers, textures);

This is done three times:

glBindTexture(GL_TEXTURE_2D, textures[targetBuffer]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, colorType, width, height, 0, colorFormat, colorDataType, NULL);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + targetBuffer, GL_TEXTURE_2D, textures[targetBuffer], 0);
targetBuffer++;

Then I create the Depth Attachment:

glGenTextures(1, &renderBuffer);
glBindTexture(GL_TEXTURE_2D, renderBuffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32F, width, height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, renderBuffer, 0);

EDIT 2: Forgot the last bit of the FBO:

GLenum *DrawBuffers = new GLenum[numBuffers];
for (size_t i = 0; i < numBuffers; i++)
    DrawBuffers[i] = GL_COLOR_ATTACHMENT0 + i;

glDrawBuffers(numBuffers, DrawBuffers);

// Report errors
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE) {
    fprintf(stderr, "Framebuffer Error. Status 0x%x\n", status);
}

// Unbind
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);

Finally, my drawing (all calculations for geometry shader happens before this):

geometryShader->Use();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
graphicsWrapper->render(Geometry);

int val[3] = { 0,1,2 };
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
deferredShader->Use();

glActiveTexture(GL_TEXTURE0 + 0);
glBindTexture(GL_TEXTURE_2D, textures[0]);
glActiveTexture(GL_TEXTURE0 + 1);
glBindTexture(GL_TEXTURE_2D, textures[1]);
glActiveTexture(GL_TEXTURE0 + 2);
glBindTexture(GL_TEXTURE_2D, textures[2]);

// I use this system so it's compatible with Uniform Buffer
//       Objects and the rendering code of other graphics languages
deferredShader->PassData(&val);
deferredShader->SetInteger();
deferredShader->SetInteger();
deferredShader->SetInteger();

glClear(GL_COLOR_BUFFER_BIT);

vaoQuad->Bind();
graphicsWrapper->DrawVertexArray(4);
vaoQuad->Unbind();

Note that my code is much more object oriented than this, and I had to take a lot of this code out of context. My question is, why does attaching the depth attachment to the framebuffer cause the framebuffer to blank, while removing it works, and how do I fix it?

EDIT: I know that it's not a renderbuffer, I just called the depth texture that because it USED to be a renderbuffer, and I forgot to change the name.

derhass derhass · Accepted Answer · 2016-12-28T18:23:54

When you don't have a depth buffer, every fragment will automatically pass the depth test. Now after you add a depth buffer, the depth test will be effective (assuming you enabled it). However, yo forgot to clear your depth buffer:

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);

You clear the default framebuffer's color and depth buffer (or another FBO, it that is bound at that time), but not the depth buffer of fbo here...

There is a high chance that you depth texture is initially all zeros. With default depth conventions, that means it is already the nearest value, so the depth test will likely fail for anything you draw.

OpenGL: Depth Attachment breaks Framebuffer

1 Answers