Depth_Stencil problem on Radeon 4850

[BionicBytes]

My deferred engine developed on Geforce 8 is displaying weird stippling artifacts all over the screen on the Radeon 4850 with Cat 9.2 (Open GL 2.1 context). No issue with nVidia, but horrible grainy pattern on the Radeon. I have tracked this down to the full screen lighting phase of the deferred renderer where I enable stencil test and then copy a full screen quad.
I suspect that ATI are not properly supporting the DEPTH24_STENCIL8 as part of the Framebuffer.

Has anyone else used D24_S8 on the Radeon 4xxx ?

On a similar note, has anyone got a quick way to 'see' the contents of the stencil buffer. I.e. copy the stencil to a texture so I can visualise it's contents.

[martinsm]

Yeah, I am getting same defect on HD2400 with my deferred rendering. Also DEPTH32F_STENCIL8 doesn't help. Only thing that helps is not using stencil.

[NULL_PTR]

On a similar note, has anyone got a quick way to 'see' the contents of the stencil buffer. I.e. copy the stencil to a texture so I can visualise it's contents.

You can try GL_NV_copy_depth_to_color, AMD added this extension in their Catalyst 9.2.

Has anyone else used D24_S8 on the Radeon 4xxx ?

Working fine on Radeon 4850 with both Catalyst 9.1 and 9.2.

[BionicBytes]

NULL_PRT: Thanks for the NV_ext tip.
Are you saying my setup code for depth_stencil texture is wrong?

During the lighting pahse of the derferred engine, I copy the MRT colour texture to the target framebuffer, but select only pixels tagged as "do not light" using a stencil ref value of $01.

bind framebuffer...
set 2D matricies...
glclearcolor (0.0, 0.0, 0.0, 0.0);
glclear (GL_COLOR_BUFFER_BIT);
glenable (GL_STENCIL_TEST);

glStencilFunc (GL_EQUAL, $01, $FF); //pass stencil test if the ref value (equal) to stencil buffer
glStencilOp (GL_KEEP,GL_KEEP, GL_KEEP);
bind MRT colour texture
draw full screen quad

Next, I render the directional lights are a full screen quad...with add blending...

glenable (GL_STENCIL_TEST);
glStencilFunc (GL_EQUAL, $08, $FF); //pixel to be lit are $08
glStencilOp (GL_KEEP,GL_KEEP, GL_KEEP);
glenable (GL_BLEND);
glblendequation (GL_FUNC_ADD);
glblendfunc (GL_ONE, GL_ONE);
glcolor4f (1,1,1,0.7);
bind all three MRT textures ....
enable DirectionalLight shader....
set light uniform params...
draw full screen quad...
disable shader...
unbind framebuffer...

The problem, however, is starting with the fixed function texture copy with stencil enabled.
Disabling the stencil - then I don't have any stippling artifacts.

NULL_PTR: Can I clarify - are you using depth_stencil texture as part of the framebuffer (or are you using stencil and depth render buffers)?

Considering how all this code works very well on the Geforce 8 - I can't see how it can be wrong on the Radeon. I've also placed in my code extensive checking with glGetError and check at every phase of the rendering (GBuffer, Lighting, Refraction, Reflection, Transparency, postprocess). No errors.

Looking at my Depth_Stencil texture creation code.. it looks like I use:

glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH24_STENCIL8_EXT, sizeX, sizeY, 0, GL_DEPTH_STENCIL_EXT, GL_UNSIGNED_INT_24_8, nil );

and use GL_LINEAR for min and mag filtering.

Any suggestions with stencil or stencil buffer creation?

[NULL_PTR]

NULL_PTR: Can I clarify - are you using depth_stencil texture as part of the framebuffer (or are you using stencil and depth render buffers)?

I do use depth\stencil render buffer instead of a texture to bind to FBO.

Now I've replaced render buffer with texture and I can see some artifacts, similar to what you've described.

[BionicBytes]

...I thought so. Now I'll have to rearchitect the engine so that shared depth_stencil can be buffers as well as a texture. Oh hum.

NULL_PTR: Do you use the same bufferID when creating the depth buffer and stencil or are you using separate bufferID?
Here's my code - but this is not tested w.r.t stencil.

glGenRenderbuffers( 1, @FrameBuffers[bufferID].FBDepth ); // allocate shared Depth render target.
glBindRenderbuffer( GL_RENDERBUFFER, FrameBuffers[bufferID].FBDepth );
glRenderbufferStorage( GL_RENDERBUFFER, Template.DepthFormat, FBWidth , FBHeight );
glFramebufferRenderbuffer(GL_FRAMEBUFFER,GL_DEPTH_ ATTACHMENT,GL_RENDERBUFFER, FrameBuffers[bufferID].FBDepth);

glGenRenderbuffers( 1, @FrameBuffers[bufferID].FBstencil ); // allocate shared stencil render target.
glBindRenderbuffer(GL_RENDERBUFFER, FrameBuffers[bufferID].FBstencil);
glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX, FBwidth , FBheight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER,GL_STENCI L_ATTACHMENT,GL_RENDERBUFFER, FrameBuffers[bufferID].FBstencil);

I'd appreciate your comments as the stencil code may be wrong.

[NULL_PTR]

Do you use the same bufferID when creating the depth buffer and stencil or are you using separate bufferID?

Here's my code that yields correct results:
//Render buffer creation
glGenRenderbuffers(1, &depthStencil);
glBindRenderbuffer(GL_RENDERBUFFER, depthStencil);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8_EXT, width, height);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

// FBO setup
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthStencil);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthStencil);

[martinsm]

I have tried also depth_stencil renderbuffer instead of texture.
After geometry pass I copy using glBlitFramebuffer from these renderbuffers depth value to texture so I can sample values out of it in lighting pass. But it didn't help - I still see bad artifacts. I think problem is in reading value out of depth_stencil texture not rendering into it. Because geometry pass yields correct results - depth is not corrupted.

[BionicBytes]

Looks like separate render buffers are the way to go on ATI...thanks Null_PTR.

martinsm: I've had issues with framebufferBlit - I can't get it to do anything. No errors - just no copying! yet it seems intuative enough. Have you an example you can post for me ?

[martinsm]

Blitting works fine for me on ATI.

glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, fbo_handle_to_read_from);
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT); // from which attachment read
glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fbo_handle_to_write_to);
glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT); // to which attachment write
glBlitFramebufferEXT(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

Note that you can use 0 as fbo_handle for bindFramebufferExt to indicate that you want to read/write to window system provided framebuffer.