I'm trying to get the depth buffer for my 2D game working by offsetting the z value of the rectangles. For some reason, my depth buffer is coming back empty. The value is always 0. I'm assuiming there is something wrong with how I attach the depth buffer to the FBO? But I've looked over that code many times and don't see anything wrong with it. Let me know if you need more information.

• I have depth testing enabled with GL_LEQUAL.
• I have znear and zfar set to 1.f, -10.f and I have 9 quads setup at three different depths.

FBO setup:

RenderTarget::RenderTarget(int width, int height) {
    
    mWidth = width;
    mHeight = height;
    mVbo = 0;

    // Create the color buffer
    glGenTextures(1, &mTextureId);
    glBindTexture(GL_TEXTURE_2D, mTextureId);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, mWidth, mHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);


    // Create the depth buffer
    glGenTextures(1, &mDepth);
    glBindTexture(GL_TEXTURE_2D, mDepth);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32, mWidth, mHeight, 0, GL_RED, GL_BYTE, NULL);

    /*glGenRenderbuffers(1, &mDepth);
    glBindRenderbuffer(GL_RENDERBUFFER, mDepth);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT32, mWidth, mHeight);*/
    
    // Create the frame buffer
    glGenFramebuffers(1, &mFbo);
    glBindFramebuffer(GL_FRAMEBUFFER, mFbo);
    
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, mTextureId, 0);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, mDepth, 0);

    

    GLenum err = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    assert(err == GL_FRAMEBUFFER_COMPLETE);
    
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    createVbo();
}

Fragment shader

#version 120

uniform sampler2D diffuseMap;
uniform sampler2D lightmap;
uniform sampler2D depthMap;

varying vec4 texCoord[2];

void main()
{
    vec4 color = texture2D(diffuseMap, gl_TexCoord[0].st);
    vec4 light = texture2D(lightmap, gl_TexCoord[0].st);
    vec4 depth = texture2D(depthMap, gl_TexCoord[0].st);

    vec4 final = color * vec4(0.1);
    final += color * light;
    gl_FragColor= vec4(depth.r, depth.r, depth.r, 1.0);
}

Method to draw sprites to the screen/framebuffer

void GraphicsDevice::drawSprite(ISprite *sprite, float x, float y, float z, Material::TextureType type, Color c) {
    
    glActiveTexture(GL_TEXTURE0);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    
    glBindBuffer(GL_ARRAY_BUFFER, sprite->getVbo());
    
    glBindTexture(GL_TEXTURE_2D, sprite->getMaterial()->getTexture(type)->getId());

    glPushMatrix();
    glTranslatef(x, y, z);
    glColor4f(c.r, c.g, c.b, c.a);

    glVertexPointer(3, GL_FLOAT, sizeof(Vertex), (void*)offsetof(Vertex, x));
    glTexCoordPointer(2, GL_FLOAT, sizeof(Vertex), (void*)offsetof(Vertex, tx));

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    
    glPopMatrix();

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_VERTEX_ARRAY);

}