Depth Test(?) help
Post: #1
I've written a basic OpenGL app that has a camera and 2 quads drawn. My problem is that I don't think depth testing is working properly, or perhaps I have something else flawed.
In my scene, I have a red quad and a green quad. The red quad is in front of the green quad (when facing down Z from 0,0,0).
(Default View - Looking Down Z)
![[Image: idg_01.jpg]](http://www.hunterinteractive.com/personal/idg_01.jpg)
As you can see in this image, the green quad appears to be in front of the red quad. This shouldn't be so.
(Perspective View)
![[Image: idg_02.jpg]](http://www.hunterinteractive.com/personal/idg_02.jpg)
Again, the green quad appears in front of the red quad.
(Opposite View - Looking Up Z)
![[Image: idg_03.jpg]](http://www.hunterinteractive.com/personal/idg_03.jpg)
Now that I look at everything from the opposite side, the red quad appears behind the green quad as it should.
Below is related code:
Can someone please tell me what I'm doing wrong?
Thanks for any help you can offer.
In my scene, I have a red quad and a green quad. The red quad is in front of the green quad (when facing down Z from 0,0,0).
(Default View - Looking Down Z)
As you can see in this image, the green quad appears to be in front of the red quad. This shouldn't be so.
(Perspective View)
Again, the green quad appears in front of the red quad.
(Opposite View - Looking Up Z)
Now that I look at everything from the opposite side, the red quad appears behind the green quad as it should.
Below is related code:
Code:
-(void)prepareOpenGL
{
long swapInt = 1;
[[self openGLContext] setValues:&swapInt forParameter:NSOpenGLCPSwapInterval]; // set to vbl sync
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL); //ive tried GL_LESS, and GL_GREATER also
glEnable(GL_TEXTURE_2D);
glEnable(GL_COLOR_MATERIAL);
glShadeModel(GL_SMOOTH);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glPolygonOffset(1.0f, 1.0f);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClearDepth(1.0);
}
-(void)drawScene
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//...setup view...
glPushMatrix();
glBegin(GL_QUADS);
//fr
glColor3f(1.0,0.0,0.0);
glVertex3d(-1.0,-1.0,1.0);
glVertex3d(1.0,-1.0,1.0);
glVertex3d(1.0,1.0,1.0);
glVertex3d(-1.0,1.0,1.0);
//ba
glColor3f(0.0,1.0,0.0);
glVertex3d(-1.0,-1.0,-1.0);
glVertex3d(1.0,-1.0,-1.0);
glVertex3d(1.0,1.0,-1.0);
glVertex3d(-1.0,1.0,-1.0);
glEnd();
glPopMatrix();
glFlush();
}Can someone please tell me what I'm doing wrong?
Thanks for any help you can offer.
Post: #3
Oops I forgot to include my pixel format in my first post:
16 is a valid value for depth size right?
Code:
NSOpenGLPixelFormatAttribute attributes [] = {
//NSOpenGLPFAWindow,
NSOpenGLPFADoubleBuffer, // double buffered
NSOpenGLPFAAccelerated,
NSOpenGLPFAColorSize, (NSOpenGLPixelFormatAttribute)16, // 16 bit color buffer
NSOpenGLPFADepthSize, (NSOpenGLPixelFormatAttribute)16, // 16 bit depth buffer
(NSOpenGLPixelFormatAttribute)nil
};16 is a valid value for depth size right?
Post: #4
Well, I think I may know what the problem is. I'm using Apple's CustomOpenGLView (verbatim) and my own subclass of the view. Oddly, CustomOpenGLView is a subclass of NSView (as opposed to NSOpenGLView). Perhaps someone could take a look at it to see if everything is up to par?
Project File:
ftp://ftp.apple.com/developer/Sample_Cod...OpenGL.sit
Project Page:
http://developer.apple.com/samplecode/Sa...OpenGL.htm
Project File:
ftp://ftp.apple.com/developer/Sample_Cod...OpenGL.sit
Project Page:
http://developer.apple.com/samplecode/Sa...OpenGL.htm
Post: #5
That seems like it should work.
As a quick sanity check, can you get the depth buffer size back from the context just before you draw to it?
As a quick sanity check, can you get the depth buffer size back from the context just before you draw to it?
Post: #6
Ahh yes. GL_DEPTH_RANGE appears to be 0 before I draw my scene...so this is the problem. Apple's code in BasicOpenGLView (subclass of CustomOpenGLView [subclass of NSView]: this is what I modeled my custom view after) appears to be messed. For some reason, it's not getting/asking for the pixel format. Hmm.
Post: #8
AnotherJake: I've never used it either, I just figured I'd throw it in there since it's in Apple's code. I have no clue what it does either.
Anyway, it turns out I didn't have my view set up properly in InterfaceBuilder and as a result, the pixelFormat function wasn't getting called. Now that I got it set up the right, I get nothing by white in the view (using the same pixelFormat above). So from this, I can conclude that when I pass an EMPTY pixelFormat to my context, everything is normal except that there is no depth testing. But if I pass a PROPER pixelFormat to my context, I get nothing but white, even though the clear color is black. Any ideas?
OSC: When I call glGetIntegerv on GL_DEPTH_BITS (before I fixed the IB thing: when the context was getting an empty pixelFormat), I would get 0. Now that I am passing a proper pixelFormat to the context, I get 16 (as I should), but again, everything is white.
Anyway, it turns out I didn't have my view set up properly in InterfaceBuilder and as a result, the pixelFormat function wasn't getting called. Now that I got it set up the right, I get nothing by white in the view (using the same pixelFormat above). So from this, I can conclude that when I pass an EMPTY pixelFormat to my context, everything is normal except that there is no depth testing. But if I pass a PROPER pixelFormat to my context, I get nothing but white, even though the clear color is black. Any ideas?
OSC: When I call glGetIntegerv on GL_DEPTH_BITS (before I fixed the IB thing: when the context was getting an empty pixelFormat), I would get 0. Now that I am passing a proper pixelFormat to the context, I get 16 (as I should), but again, everything is white.
Possibly Related Threads...
| Thread: | Author | Replies: | Views: | Last Post | |
| depth test feedback | honkFactory | 6 | 3,098 |
Feb 20, 2003 08:12 PM Last Post: OneSadCookie |
|