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Depth Buffer Issues? (Pic Inside)

Started by datadawgx May 22, 2006 at 8:27 PM 5 replies 950+ views

Original Post

May 22, 2006 at 8:27 PM

Hey guys, I'm having a wierd depth buffer problem. I am drawing a simple city and buildings are sometimes (not always) showing up in the wrong order(farthest buildings show in front of closer buildings). Below is an image of the problem: http://www.seanazlin.com/images/wtf.jpg

You'll notice that bldg 3 shows up in front of bldg 1 and 2, and 2 shows up in front of 1. We should be seeing 1, 2, and then 3 from closest to farthest. In the center of the screen I have 2 towers that are also showing up in the wrong order. I'm thinking something is wrong with my render states. Here's what I am setting:


g_pdevice->SetRenderState(D3DRS_ZENABLE,  TRUE ); // Z-Buffer (Depth Buffer)
g_pdevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW ); 
g_pdevice->SetRenderState(D3DRS_LIGHTING, FALSE);
g_pdevice->SetRenderState(D3DRS_AMBIENT,  D3DCOLOR_XRGB(180, 180, 180));
g_pdevice->SetRenderState( D3DRS_FILLMODE, D3DFILL_SOLID);
...
g_pdevice->BeginScene();
g_city1.Render(g_pdevice);
g_pdevice->EndScene();

this isnt all of the source, but it is all of the render states. i've tried messing with everything and looking through the sdk with no success. Anyone have an idea of what's going wrong? -Sean

ViLiO

May 22, 2006 at 8:31 PM

Having a znear of 0.0 could cause this problem. What is your device's projection matrix set to?

Regards,
ViLiO

datadawgx

May 22, 2006 at 9:09 PM

good call. I know not to set it to 0, but I was setting it to 0.001... and that turns out to be the prob. Setting it to 0.01 fixed it.

thanks. =)

Evil Steve

May 23, 2006 at 3:28 AM

Quote:
Original post by datadawgx
good call. I know not to set it to 0, but I was setting it to 0.001... and that turns out to be the prob. Setting it to 0.01 fixed it.

thanks. =)

I wouldn't even set it that low. If you're rendering on that sort of scale (Assuming the buildings are a few hundred to a few thousand units high), I'd set the front clipping plane to at least 1.0f. I don't remember the exact numbers, but something like 75% of the z-buffer accuracy is used in the first 25% of the range.

Boder

May 23, 2006 at 3:42 AM

Z-buffer: the Nitty-Gritty by LeGreg

QuadMV

May 23, 2006 at 9:24 AM

You might also consider changing the z-near based on the environment. For example when indoors you might want to get very close to the wall and set it small, but since your site range is less indoor, you can set z-far smaller. When outdoors you'll bump them both up. This isn't perfect, but can provide benefit.

Thergothon

May 23, 2006 at 11:33 AM

EDIT: beaten. didnt realise you fixed it already.

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