Depth testing not working openGL ES

Question

I have a cube which i'm drawing on screen, i have activated the depth testing in order for it not to be transparent, the thing is, in the front and back side of the cube, it look's good. but when translating and rotating the cube, the results are strange, here are some photos to demonstrate:

front:

sides:

This see through effect is not welcomed of course.

Here is some relevant code:

Indices & vertices:

const Vertex Vertices[] = {
    {{1, -1, 0}, {1, 1, 1, 1}, {1, 0}},
    {{1, 1, 0}, {1, 1, 1, 1}, {1, 1}},
    {{-1, 1, 0}, {1, 1, 1, 1}, {0, 1}},
    {{-1, -1, 0}, {1, 1, 1, 1}, {0, 0}},
    {{1, -1, -1}, {1, 1, 1, 1}, {1, 0}},
    {{1, 1, -1}, {1, 1, 1, 1}, {1, 1}},
    {{-1, 1, -1}, {1, 1, 1, 1}, {0, 1}},
    {{-1, -1, -1}, {1, 1, 1, 1}, {0, 0}}
};

const GLubyte Indices[] = {
    // Front
    0, 1, 2
    ,2, 3, 0,
    // Back
    4, 6, 5,
    4, 7, 6,
    // Left
    2, 7, 3,
    7, 6, 2,
    // Right
    0, 4, 1,
    4, 1, 5,
    // Top
    6, 2, 1,
    1, 6, 5,
    // Bottom
    0, 3, 7,
    0, 7, 4,
};

Layer setup:

- (void)setupLayer {
    _eaglLayer = (CAEAGLLayer*) self.layer;
    _eaglLayer.opaque = YES;
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_NEVER);
}

Depth buffer setup:

- (void)setupDepthBuffer {
    glGenRenderbuffers(1, &_depthRenderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, self.frame.size.width, self.frame.size.height);
}

Rendering:

- (void)render:(CADisplayLink*)displayLink {
    glClearColor(0, 0, 0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);

    CC3GLMatrix *projection = [CC3GLMatrix matrix];
    float h = 4.0f * self.frame.size.height / self.frame.size.width;
    [projection populateFromFrustumLeft:-2 andRight:2 andBottom:-h/2 andTop:h/2 andNear:4 andFar:10];
    glUniformMatrix4fv(_projectionUniform, 1, 0, projection.glMatrix);

    CC3GLMatrix *modelView = [CC3GLMatrix matrix];
    [modelView populateFromTranslation:CC3VectorMake(sin(CACurrentMediaTime()), 0, -5)];
    _currentRotation += displayLink.duration * 90;
    [modelView rotateBy:CC3VectorMake(_currentRotation, _currentRotation, 0)];
    glUniformMatrix4fv(_modelViewUniform, 1, 0, modelView.glMatrix);

    glViewport(0, 0, self.frame.size.width, self.frame.size.height);

    glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), 0);
    glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), (GLvoid*) (sizeof(float)* 3));
    glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE,
                          sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));


    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, _floorTexture);
    glUniform1i(_textureUniform, 0);

    glDrawElements(GL_TRIANGLE_STRIP, sizeof(Indices)/sizeof(Indices[0]),
                   GL_UNSIGNED_BYTE, 0);

    [_context presentRenderbuffer:GL_RENDERBUFFER];
}

EDIT:

adding the texture mapping function:

- (GLuint)setupTexture:(NSString *)fileName {
    // 1
    CGImageRef spriteImage = [UIImage imageNamed:fileName].CGImage;
    if (!spriteImage) {
        NSLog(@"Failed to load image %@", fileName);
        exit(1);
    }

        // 2
    size_t width = CGImageGetWidth(spriteImage);
    size_t height = CGImageGetHeight(spriteImage);


    GLubyte * spriteData = (GLubyte *) calloc(width*height*4, sizeof(GLubyte));


    CGContextRef spriteContext = CGBitmapContextCreate(spriteData, width, height, 8, width*4,
                                                       CGImageGetColorSpace(spriteImage), kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    // 3
    CGContextDrawImage(spriteContext, CGRectMake(0, 0, width, height), spriteImage);

    CGContextRelease(spriteContext);

    // 4
    GLuint texName;
    glGenTextures(1, &texName);
    glBindTexture(GL_TEXTURE_2D, texName);

    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_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);

    free(spriteData);  
    return texName;    
}

What am i doing wrong over here?

Answer 1

glDepthFunc(GL_NEVER); - at least replace this with GL_LEQUAL .