Z axis, Z Cache

The second method of deep sorting is the Z-buffer method, which is the most commonly used method for graphics hardware devices. This method depends on pixels. Each pixel has a Z value (the Z value is the distance between the pixel and the observer ). When each pixel is written, the Renderer first checks whether a pixel with a smaller Z value exists. If it does not exist, the pixel is drawn. If it exists, the pixel is skipped.

Many 3D graphics acceleration cards have a built-in Z buffer, which is also the reason for choosing the Z buffer method for deep sorting. The easiest way to use the Z buffer in an application is to initialize the Z buffer when creating a device object and setting the display mode, as shown below:

View Source

Print?

01	D3DPRESENT_PARAMETERS d3dpp;

02	ZeroMemory(&d3dpp, sizeof(d3dpp));

03	d3dpp.Windowed                = TRUE;

04	d3dpp.SwapEffect              = D3DSWAPEFFECT_DISCARD;

05	d3dpp.BackBufferFormat        = d3ddm.Format;

06	// Set the Z buffer and the Z buffer format.

07	d3dpp.EnableAutoDepthStencil  = TRUE;

08	d3dpp.AutoDepthStencilFormat  = D3DFMT_D16;

09

10	if(FAILED(g_pD3D->CreateDevice(D3DADAPTER_DEFAULT,D3DDEVTYPE_HAL,g_hWnd,

11	D3DCREATE_SOFTWARE_VERTEXPROCESSING, &d3dpp, &g_pD3DDevice)))

12	return FALSE;

13

14	// Set the rendering states

15	g_pD3DDevice->SetRenderState(D3DRS_LIGHTING, FALSE);

16	g_pD3DDevice->SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);

At the same time, idirect3ddevice9: Clear should be used to clear the Z cache before each frame is drawn.

View Source

Print?

1	// clear device back buffer

2	g_d3d_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_RGBA(0, 0, 0, 255), 1.0f, 0);

In fact, this is because of Z-test. When rendering a polygon mesh object to a scenario, the object that is farther away from the observer should be blurred, and the object that is closer to the observer should be clearer. This is the depth sorting ).