在DirectX程序中我们可以设置多个不同的视口用于显示不同的图形，每个视口都可以清空和独立绘制。渲染目标表面的深度值范围（通常是0.0到 1.0），在这之间的物体会被渲染。
我们先看以下处理多个视口的代码:
//********************************************************************
// Filename: Main.cpp
// Author: Chinafish
// Modifier: Chinafish
// Created: 2010-06-25 12:16
// Updated: 2010-06-25 12:16
// QQ: 149200849
// MSN: china_fish@msn.com
// Purpose: Set multiple view ports.
//====================================================================
// Copyright(C) 2004-2010 by Chinafish. All Rights Reserved.
//********************************************************************
#define STRICT
#define WIN32_LEAN_AND_MEAN
#include "windows.h"
// Link D3D
#include "d3d9.h"
#pragma comment(lib, "d3d9.lib")
#define Release_Safe(p){if(p!=NULL) p->Release();}
#define WINDOW_TITLE "www.csinx.org - Multiple Viewports (DX9+VC7)"
#define WINDOW_WIDTH 800
#define WINDOW_HEIGHT 600
//-----------------------------------------------------------------------------
// GLOBALS
//-----------------------------------------------------------------------------
HWND g_hWnd = NULL;
LPDIRECT3D9 g_pD3D = NULL;
LPDIRECT3DDEVICE9 g_pd3dDevice = NULL;
D3DPRESENT_PARAMETERS g_d3dpp;
DWORD g_dwBackBufferWidth = 0;
DWORD g_dwBackBufferHeight = 0;
//-----------------------------------------------------------------------------
// PROTOTYPES
//-----------------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow);
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
void InitD3D();
HRESULT RestoreDeviceObjects();
HRESULT InvalidateDeviceObjects();
void ShutDown(void);
void Render(void);
//-----------------------------------------------------------------------------
// Name: WinMain()
// Desc: The application's entry point
//-----------------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX winClass;
MSG uMsg;
memset(&uMsg,0,sizeof(uMsg));
winClass.lpszClassName = "CLASS_MULTIPLEVIEWPORTS";
winClass.cbSize = sizeof(WNDCLASSEX);
winClass.style = CS_HREDRAW | CS_VREDRAW;
winClass.lpfnWndProc = WindowProc;
winClass.hInstance = hInstance;
winClass.hIcon = LoadIcon(hInstance, (LPCTSTR)NULL);
winClass.hIconSm = LoadIcon(hInstance, (LPCTSTR)NULL);
winClass.hCursor = LoadCursor(NULL, IDC_ARROW);
winClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winClass.lpszMenuName = NULL;
winClass.cbClsExtra = 0;
winClass.cbWndExtra = 0;
if(!RegisterClassEx(&winClass))
return E_FAIL;
g_hWnd = CreateWindowEx(NULL, "CLASS_MULTIPLEVIEWPORTS",
WINDOW_TITLE,
WS_EX_TOPMOST, 0, 0,
WINDOW_WIDTH, WINDOW_HEIGHT, NULL, NULL,
hInstance, NULL);
if(g_hWnd == NULL)
return E_FAIL;
// Adjust window
RECT rect = { 0, 0, WINDOW_WIDTH, WINDOW_HEIGHT };
AdjustWindowRect(&rect, GetWindowLong(g_hWnd, GWL_STYLE), FALSE);
SetWindowPos(g_hWnd, 0, 0, 0, rect.right - rect.left, rect.bottom - rect.top,
SWP_NOZORDER | SWP_NOMOVE);
ShowWindow(g_hWnd, nCmdShow);
UpdateWindow(g_hWnd);
// Init or reset D3D
InitD3D();
while(uMsg.message != WM_QUIT)
{
if(PeekMessage(&uMsg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&uMsg);
DispatchMessage(&uMsg);
}
else
{
// Render a frame
Render();
}
}
ShutDown();
UnregisterClass("CLASS_MULTIPLEVIEWPORTS", winClass.hInstance);
return uMsg.wParam;
}
//-----------------------------------------------------------------------------
// Name: WindowProc()
// Desc: The window's message handler
//-----------------------------------------------------------------------------
LRESULT CALLBACK WindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_KEYDOWN:
{
switch(wParam)
{
case VK_ESCAPE:
PostQuitMessage(0);
break;
}
}
break;
case WM_CLOSE:
{
PostQuitMessage(0);
}
case WM_DESTROY:
{
PostQuitMessage(0);
}
break;
default:
{
return DefWindowProc(hWnd, msg, wParam, lParam);
}
break;
}
return 0;
}
//-----------------------------------------------------------------------------
// Name: InitD3D()
// Desc: This function will only be called once during the application's
// initialization phase. Therefore, it can't contain any resources that
// need to be restored every time the Direct3D device is lost or the
// window is resized.
//-----------------------------------------------------------------------------
void InitD3D()
{
// Create D3D
g_pD3D = Direct3DCreate9(D3D_SDK_VERSION);
if(!g_pD3D)
{
MessageBox(NULL, "Direct3DCreate9() - Failed!", "Error", NULL);
return;
}
D3DDISPLAYMODE d3ddm;
g_pD3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &d3ddm);
ZeroMemory(&g_d3dpp, sizeof(g_d3dpp));
g_d3dpp.Windowed = TRUE;
g_d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
g_d3dpp.BackBufferFormat = d3ddm.Format;
g_d3dpp.EnableAutoDepthStencil = TRUE;
g_d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
g_d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;
g_pD3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL,
g_hWnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&g_d3dpp, &g_pd3dDevice);
if(!g_pd3dDevice)
{
return;
}
//
// Cache the width & height of the back-buffer...
//
LPDIRECT3DSURFACE9 pBackBuffer = NULL;
D3DSURFACE_DESC d3dsd;
g_pd3dDevice->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO, &pBackBuffer);
pBackBuffer->GetDesc(&d3dsd);
pBackBuffer->Release();
g_dwBackBufferWidth = d3dsd.Width;
g_dwBackBufferHeight = d3dsd.Height;
// Any resources or settings that need to be restored after losing the
// DirectX device should probably be grouped together into one function so
// they can be re-created or reset in one call.
RestoreDeviceObjects();
}
//-----------------------------------------------------------------------------
// Name: RestoreDeviceObjects()
// Desc: You are encouraged to develop applications with a single code path to
// respond to device loss. This code path is likely to be similar, if not
// identical, to the code path taken to initialize the device at startup.
//-----------------------------------------------------------------------------
HRESULT RestoreDeviceObjects()
{
// Set some important state settings...
// Set Transform
// Create a texture object, mesh object, buffer etc.
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: InvalidateDeviceObjects()
// Desc: If the lost device can be restored, the application prepares the
// device by destroying all video-memory resources and any
// swap chains. This is typically accomplished by using the SAFE_RELEASE
// macro.
//-----------------------------------------------------------------------------
HRESULT InvalidateDeviceObjects()
{
// Invalidate the texture object, mesh object, buffer etc.
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: ShutDown()
// Desc: Release all
//-----------------------------------------------------------------------------
void ShutDown(void)
{
InvalidateDeviceObjects();
Release_Safe(g_pd3dDevice);
Release_Safe(g_pD3D);
}
//-----------------------------------------------------------------------------
// Name: Render()
// Desc: Render something you want
//-----------------------------------------------------------------------------
void Render(void)
{
//
// Render to the Top-left viewport
//
D3DVIEWPORT9 tlViewPort;
tlViewPort.X = 0;
tlViewPort.Y = 0;
tlViewPort.Width = g_dwBackBufferWidth / 2;
tlViewPort.Height = g_dwBackBufferHeight / 2;
tlViewPort.MinZ = 0.0f;
tlViewPort.MaxZ = 1.0f;
g_pd3dDevice->SetViewport(&tlViewPort);
// Clear screen with D3DCOLOR_XRGB(255, 0, 0)
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(255, 0, 0), 1.0f, 0);
g_pd3dDevice->BeginScene();
// Render geometry here...
g_pd3dDevice->EndScene();
//
// Render to the Top-right viewport
//
D3DVIEWPORT9 trViewPort;
trViewPort.X = g_dwBackBufferWidth / 2;
trViewPort.Y = 0;
trViewPort.Width = g_dwBackBufferWidth / 2;
trViewPort.Height = g_dwBackBufferHeight / 2;
trViewPort.MinZ = 0.0f;
trViewPort.MaxZ = 1.0f;
g_pd3dDevice->SetViewport(&trViewPort);
// Clear screen with D3DCOLOR_XRGB(0, 255, 0)
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 255, 0), 1.0f, 0);
g_pd3dDevice->BeginScene();
// Render geometry here...
g_pd3dDevice->EndScene();
//
// Render to the Bottom-left viewport
//
D3DVIEWPORT9 blViewPort;
blViewPort.X = 0;
blViewPort.Y = g_dwBackBufferHeight / 2;
blViewPort.Width = g_dwBackBufferWidth / 2;
blViewPort.Height = g_dwBackBufferHeight / 2;
blViewPort.MinZ = 0.0f;
blViewPort.MaxZ = 1.0f;
g_pd3dDevice->SetViewport(&blViewPort);
// Clear screen with D3DCOLOR_XRGB(0, 0, 255)
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 255), 1.0f, 0);
g_pd3dDevice->BeginScene();
// Render geometry here...
g_pd3dDevice->EndScene();
//
// Render to the Bottom-right viewport
//
D3DVIEWPORT9 brViewPort;
brViewPort.X = g_dwBackBufferWidth / 2;
brViewPort.Y = g_dwBackBufferHeight / 2;
brViewPort.Width = g_dwBackBufferWidth / 2;
brViewPort.Height = g_dwBackBufferHeight / 2;
brViewPort.MinZ = 0.0f;
brViewPort.MaxZ = 1.0f;
g_pd3dDevice->SetViewport(&brViewPort);
// Clear screen with D3DCOLOR_XRGB(255, 0, 255)
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(255, 0, 255), 1.0f, 0);
g_pd3dDevice->BeginScene();
// Render geometry here...
g_pd3dDevice->EndScene();
g_pd3dDevice->Present(NULL, NULL, NULL, NULL);
}
框架代码我们在前面已经有说明，这里需要说明的是在创建设备后取到后台缓冲大小，在渲染时调用 IDirect3DDevice9::SetViewport 方法来设置四个不同的视口并在其中使用不同的颜色填充。
下图为本例代码执行效果:
