OpenGL depth test problem

Question

I've got a problem with OpenGL on mac, and I think the problem is the Depth test.

So, to my problem: Rather than explaining, I made two screenshots: My scene from far: http://c0848462.cdn.cloudfiles.rackspacecloud.com/dd2267e27ad7d0206526b208cf2ea6910bcd00b4fa.jpg And from near: http://c0848462.cdn.cloudfiles.rackspacecloud.com/dd2267e27a561b5f02344dca57508dddce21d2315f.jpg

If I do not draw the green floor, everything looks (kinda) fine. But still, like this it looks just aweful.

Here are the three codeblocks I use to set up Opengl:

+ (NSOpenGLPixelFormat*) defaultPixelFormat
{
    NSOpenGLPixelFormatAttribute attributes [] = {
        NSOpenGLPFAWindow,
        NSOpenGLPFADoubleBuffer, 
        NSOpenGLPFADepthSize, (NSOpenGLPixelFormatAttribute)16, 
        (NSOpenGLPixelFormatAttribute)nil
    };
    return [[[NSOpenGLPixelFormat alloc] initWithAttributes:attributes] autorelease];
}


- (void) prepareOpenGL
{
    NSLog(@"Preparing OpenGL");
    glClearColor( 0.0f, 0.0f, 1.0f, 1.0f );             

    glEnable(GL_TEXTURE_2D);                           

    glClearDepth(1);                                  
    glEnable(GL_DEPTH_TEST);                          

    glEnable (GL_BLEND);                              
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}

- (void)reshape
{
    NSLog(@"Reshaping view");
    glViewport( 0, 0, (GLsizei)[self bounds].size.width, (GLsizei)[self bounds].size.height);
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    gluPerspective( 45.0, [self bounds].size.width / [self bounds].size.height, 0.1f /*Nearest render distance*/, 5000.0 /*Render distance*/);
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
}

Thanks for asking this question. I couldn't figure out, for the life of me, why GL_DEPTH_TEST wasn't working. After I overrided defaultPixelFormat and set the depth size, it started working. — orangething, Jun 04 '12 at 14:11

score 4 · Accepted Answer · answered Jul 08 '11 at 20:53

gluPerspective( 45.0, [self bounds].size.width / [self bounds].size.height, 0.1f /*Nearest render distance*/, 5000.0 /*Render distance*/);

That's way too small of a near clip plane. The closer your near clip value is to 0, the less precision you get on values that are farther away. Push your near clip back to at least 1.0, if not farther. In general, you should push it back as far away as you can live with.

Oh, and you should be using a 24-bit depth buffer, not 16-bit.

OpenGL depth test problem

1 Answers1