Hi all, does anyone know how to implement a z-buffer with Direct Draw? thanks

here is some code


///////////////////////////////////////////////////////////
HRESULT hr;

//get the size of the soon to be zbuffer
DDSURFACEDESC2 ddsd;
_DDRAW_INIT_STRUCT(ddsd);
lpddsback->GetSurfaceDesc(&ddsd);

ddsd.dwFlags = DDSD_WIDTH | DDSD_HEIGHT | DDSD_CAPS | DDSD_PIXELFORMAT;
ddsd.ddsCaps.dwCaps = DDSCAPS_ZBUFFER | DDSCAPS_VIDEOMEMORY;
ddsd.ddpfPixelFormat.dwSize = 0;


//now enumerate the z buffer formats
lpd3d7->EnumZBufferFormats(*lpdevGUID,ZBufferEnumCallback,(void*)&ddsd.ddpfPixelFormat);

if(ddsd.ddpfPixelFormat.dwSize == 0)
{
//return some error here cause no formats were found;
}

//create and attach the z buffer
if(FAILED(hr = this->lpdd7->CreateSurface(&ddsd,&lpddszbuffer,NULL)))
{
return hr;
}

if(FAILED(hr = this->lpddsback->AddAttachedSurface(lpddszbuffer)))
{
return hr;
}
////////////////////////////////////////////////////////////

You have to write your own Callback function to accept or reject the zbuffer formats that were found when enumerating them. here is a simple one


HRESULT CALLBACK ZBufferEnumCallback(DDPIXELFORMAT *lpddpf, LPVOID lpcontext)
{
DDPIXELFORMAT *lpddpf_prim = (DDPIXELFORMAT*)lpcontext;

//if the pixel format of the zbuffer equals the current colordepth, then ok
if(lpddpf_prim->dwRGBBitCount == lpddpf->dwRGBBitCount)
{
memcpy(lpcontext,lpddpf,sizeof(DDPIXELFORMAT));
return D3DENUMRET_CANCEL;
}

//gets here if there is a confirm func but this one did not pass
return D3DENUMRET_OK;
}


Then, when all is said and done.. you should do this...

lpd3ddevice7->SetRenderTarget(lpddsback). I forgot to do this after attaching my zbuffer to the back buffer and D3D did not know the zbuffer was there.. It drove me nuts for a couple days.

that should do it. you can toggle whether D3D uses the zbuffer by the following

lpd3ddevice7->->SetRenderState(D3DRENDERSTATE_ZENABLE, D3DZB_TRUE);


enjoy,

BrianH

Thank you for the answer, but I am not using Direct 3D.
I want to implement a z-buffer by software only with
Direct Draw.

Greetings

quote:Original post by ajfg

Thank you for the answer, but I am not using Direct 3D.
I want to implement a z-buffer by software only with
Direct Draw.

Greetings

Ues Overlay.

One thing you could do is to give every 2D object a z value.
Then you have to make an algorithm that draws every object in the order you want.
Lets say that you have two objects one with z value 0 and one with z value 1. Then you draw all objects with z value 0 first, then all with z value 1 and continue. Then an object with a lower z value than the other will be drawn on top of the other.