三維場景中的物體不僅受光照影響，而且受周圍環(huán)境的影響，可以映射出周圍環(huán)境的圖像，環(huán)境映射就是模擬物體光滑表面映射周圍環(huán)境的一種技術。實際上，就是將一幅包含物體周圍環(huán)境場景的紋理貼到物體表面上，這樣就可以在一定程度上模擬出物體對周圍環(huán)境的映射，而無須使用像光線跟蹤算法這種復雜的計算技術。
在圖形工業(yè)中有多種環(huán)境映射，下面介紹兩種最常用的環(huán)境映射：立方體環(huán)境映射和球形環(huán)境映射。
立方體環(huán)境映射
立方體環(huán)境映射圖有時又稱為立方體映射圖，是一組包含物體周圍環(huán)境圖像的紋理貼圖，好像物體在立方體的中心。立方體環(huán)境圖的每個面覆蓋水平和垂直方向上各90度視角區(qū)域，一共6個面，各面的方向如下圖所示：
立方體環(huán)境映射圖的6個面布局如下圖所示：
球形環(huán)境映射
球形環(huán)境映射圖（或稱為球形映射圖）和立方體環(huán)境映射圖類似，也是一幅包含周圍場景圖像的特殊紋理。和立方體環(huán)境映射圖不同的是，球形環(huán)境映射圖不直接代表物體周圍的環(huán)境。球形映射圖就好像通過魚眼（fish-eye）凸透鏡觀察到的景象一樣，是一個物體周圍環(huán)境360度全方位視域的三維表現(xiàn)。
首先使用一張球形的背景圖作為環(huán)境映射紋理，如下所示：
接著在回調函數(shù)OnCreateDevice()中加載紋理和網(wǎng)格模型：
V_RETURN(D3DXCreateTextureFromFile(pd3dDevice, L"spheremap.bmp", &g_env_texture));
ID3DXBuffer* material_buffer;
V_RETURN(D3DXLoadMeshFromXW(L"teapot.x", D3DXMESH_MANAGED, pd3dDevice, NULL, &material_buffer, NULL,
&g_num_materials, &g_mesh));
D3DXMATERIAL* xmaterials = (D3DXMATERIAL*) material_buffer->GetBufferPointer();
g_mesh_materials = new D3DMATERIAL9[g_num_materials];
for(DWORD i = 0; i < g_num_materials; i++)
{
g_mesh_materials[i] = xmaterials[i].MatD3D;
// .x file do not save ambient data, so set it here.
g_mesh_materials[i].Ambient = g_mesh_materials[i].Diffuse;
}
material_buffer->Release();
該網(wǎng)格模型的視覺效果如下所示：
接著在回調函數(shù)OnResetDevice()中自動生成紋理坐標，并設置紋理階段顏色混合方法：
// set texture color blend method, disalbe alpha blend.
pd3dDevice->SetTexture(0, g_env_texture);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_DISABLE);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_SPHEREMAP);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS,
D3DTTFF_COUNT2);
最后在回調函數(shù)OnFrameRender()中渲染茶壺：
// Clear the render target and the zbuffer
V( pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_ARGB(0, 0, 0, 0), 1.0f, 0) );
// Render the scene
if( SUCCEEDED( pd3dDevice->BeginScene() ) )
{
for(DWORD i = 0; i < g_num_materials; i++)
{
pd3dDevice->SetMaterial(&g_mesh_materials[i]);
g_mesh->DrawSubset(i);
}
RenderText();
V(g_button_dlg.OnRender(fElapsedTime));
V( pd3dDevice->EndScene() );
}
運行效果圖：
球形環(huán)境紋理映射的實現(xiàn)比較簡單，和普通紋理映射基本相同，唯一的區(qū)別是使用自動生成的球形紋理坐標。
主程序：
#include "dxstdafx.h"
#include "resource.h"
#pragma warning(disable : 4127 4995 4996)
#define release_com(p) do { if(p) { (p)->Release(); (p) = NULL; } } while(0)
#define IDC_TOGGLE_FULLSCREEN 1
#define IDC_TOGGLE_REF 2
#define IDC_CHANGE_DEVICE 3
const D3DXCOLOR FONT_COLOR(1.0f, 0.5f, 0.25f, 1.0f);
ID3DXFont* g_font;
ID3DXSprite* g_text_sprite;
bool g_show_help;
CDXUTDialogResourceManager g_dlg_resource_manager;
CD3DSettingsDlg g_settings_dlg;
CDXUTDialog g_button_dlg;
ID3DXMesh* g_mesh;
D3DMATERIAL9* g_mesh_materials;
DWORD g_num_materials;
IDirect3DTexture9* g_env_texture;
//--------------------------------------------------------------------------------------
// Rejects any devices that aren't acceptable by returning false
//--------------------------------------------------------------------------------------
bool CALLBACK IsDeviceAcceptable( D3DCAPS9* pCaps, D3DFORMAT AdapterFormat,
D3DFORMAT BackBufferFormat, bool bWindowed, void* pUserContext )
{
// Typically want to skip backbuffer formats that don't support alpha blending
IDirect3D9* pD3D = DXUTGetD3DObject();
if( FAILED( pD3D->CheckDeviceFormat( pCaps->AdapterOrdinal, pCaps->DeviceType, AdapterFormat,
D3DUSAGE_QUERY_POSTPIXELSHADER_BLENDING, D3DRTYPE_TEXTURE, BackBufferFormat ) ) )
return false;
return true;
}
//--------------------------------------------------------------------------------------
// Before a device is created, modify the device settings as needed.
//--------------------------------------------------------------------------------------
bool CALLBACK ModifyDeviceSettings( DXUTDeviceSettings* pDeviceSettings, const D3DCAPS9* pCaps, void* pUserContext )
{
// If video card does not support hardware vertex processing, then uses sofaware vertex processing.
if((pCaps->DevCaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT) == 0)
pDeviceSettings->BehaviorFlags = D3DCREATE_SOFTWARE_VERTEXPROCESSING;
static bool is_first_time = true;
if(is_first_time)
{
is_first_time = false;
// if using reference device, then pop a warning message box.
if(pDeviceSettings->DeviceType == D3DDEVTYPE_REF)
DXUTDisplaySwitchingToREFWarning();
}
return true;
}
//--------------------------------------------------------------------------------------
// Create any D3DPOOL_MANAGED resources here
//--------------------------------------------------------------------------------------
HRESULT CALLBACK OnCreateDevice( IDirect3DDevice9* pd3dDevice,
const D3DSURFACE_DESC* pBackBufferSurfaceDesc,
void* pUserContext )
{
HRESULT hr;
V_RETURN(g_dlg_resource_manager.OnCreateDevice(pd3dDevice));
V_RETURN(g_settings_dlg.OnCreateDevice(pd3dDevice));
D3DXCreateFont(pd3dDevice, 18, 0, FW_BOLD, 1, FALSE, DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, DEFAULT_QUALITY,
DEFAULT_PITCH | FF_DONTCARE, L"Arial", &g_font);
V_RETURN(D3DXCreateTextureFromFile(pd3dDevice, L"spheremap.bmp", &g_env_texture));
ID3DXBuffer* material_buffer;
V_RETURN(D3DXLoadMeshFromXW(L"teapot.x", D3DXMESH_MANAGED, pd3dDevice, NULL, &material_buffer, NULL,
&g_num_materials, &g_mesh));
D3DXMATERIAL* xmaterials = (D3DXMATERIAL*) material_buffer->GetBufferPointer();
g_mesh_materials = new D3DMATERIAL9[g_num_materials];
for(DWORD i = 0; i < g_num_materials; i++)
{
g_mesh_materials[i] = xmaterials[i].MatD3D;
// .x file do not save ambient data, so set it here.
g_mesh_materials[i].Ambient = g_mesh_materials[i].Diffuse;
}
material_buffer->Release();
return S_OK;
}
//--------------------------------------------------------------------------------------
// Create any D3DPOOL_DEFAULT resources here
//--------------------------------------------------------------------------------------
HRESULT CALLBACK OnResetDevice( IDirect3DDevice9* pd3dDevice,
const D3DSURFACE_DESC* pBackBufferSurfaceDesc,
void* pUserContext )
{
HRESULT hr;
V_RETURN(g_dlg_resource_manager.OnResetDevice());
V_RETURN(g_settings_dlg.OnResetDevice());
V_RETURN(g_font->OnResetDevice());
V_RETURN(D3DXCreateSprite(pd3dDevice, &g_text_sprite));
// set dialog position and size
g_button_dlg.SetLocation(pBackBufferSurfaceDesc->Width - 170, 0);
g_button_dlg.SetSize(170, 170);
// setup view matrix
D3DXMATRIX mat_view;
D3DXVECTOR3 eye(0.0f, 300.0f, 220.0f);
D3DXVECTOR3 at(0.0f, 0.0f, 50.0f);
D3DXVECTOR3 up(0.0f, 0.0f, 1.0f);
D3DXMatrixLookAtLH(&mat_view, &eye, &at, &up);
pd3dDevice->SetTransform(D3DTS_VIEW, &mat_view);
// set projection matrix
D3DXMATRIX mat_proj;
float aspect = (float)pBackBufferSurfaceDesc->Width / pBackBufferSurfaceDesc->Height;
D3DXMatrixPerspectiveFovLH(&mat_proj, D3DX_PI/4, aspect, 1.0f, 1000.0f);
pd3dDevice->SetTransform(D3DTS_PROJECTION, &mat_proj);
// setup material
D3DMATERIAL9 material;
ZeroMemory(&material, sizeof(D3DMATERIAL9));
material.Diffuse.r = material.Ambient.r = 1.0f;
material.Diffuse.g = material.Ambient.g = 1.0f;
material.Diffuse.b = material.Ambient.b = 1.0f;
material.Diffuse.a = material.Ambient.a = 1.0f;
pd3dDevice->SetMaterial(&material);
// setup light
D3DLIGHT9 light;
ZeroMemory(&light, sizeof(D3DLIGHT9));
light.Type = D3DLIGHT_DIRECTIONAL;
light.Diffuse.r = 1.0f;
light.Diffuse.g = 1.0f;
light.Diffuse.b = 1.0f;
light.Range = 1000.0f;
D3DXVECTOR3 light_dir(10.0f, -10.0f, -10.0f);
D3DXVec3Normalize((D3DXVECTOR3*) &light.Direction, &light_dir);
pd3dDevice->SetLight(0, &light);
pd3dDevice->LightEnable(0, TRUE);
pd3dDevice->SetRenderState(D3DRS_AMBIENT, 0x00FF8080);
// set texture color blend method, disalbe alpha blend.
pd3dDevice->SetTexture(0, g_env_texture);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_DISABLE);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_SPHEREMAP);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2);
return S_OK;
}
//--------------------------------------------------------------------------------------
// Release resources created in the OnResetDevice callback here
//--------------------------------------------------------------------------------------
void CALLBACK OnLostDevice( void* pUserContext )
{
g_dlg_resource_manager.OnLostDevice();
g_settings_dlg.OnLostDevice();
g_font->OnLostDevice();
release_com(g_text_sprite);
}
//--------------------------------------------------------------------------------------
// Release resources created in the OnCreateDevice callback here
//--------------------------------------------------------------------------------------
void CALLBACK OnDestroyDevice( void* pUserContext )
{
g_dlg_resource_manager.OnDestroyDevice();
g_settings_dlg.OnDestroyDevice();
delete[] g_mesh_materials;
g_mesh_materials = NULL;
release_com(g_font);
release_com(g_mesh);
release_com(g_env_texture);
}
//--------------------------------------------------------------------------------------
// Handle updates to the scene
//--------------------------------------------------------------------------------------
void CALLBACK OnFrameMove( IDirect3DDevice9* pd3dDevice, double fTime, float fElapsedTime, void* pUserContext )
{
}
//--------------------------------------------------------------------------------------
// Render the helper information
//--------------------------------------------------------------------------------------
void RenderText()
{
CDXUTTextHelper text_helper(g_font, g_text_sprite, 20);
text_helper.Begin();
// show frame and device states
text_helper.SetInsertionPos(5, 5);
text_helper.SetForegroundColor(FONT_COLOR);
text_helper.DrawTextLine( DXUTGetFrameStats(true) );
text_helper.DrawTextLine( DXUTGetDeviceStats() );
// show helper information
const D3DSURFACE_DESC* surface_desc = DXUTGetBackBufferSurfaceDesc();
if(g_show_help)
{
text_helper.SetInsertionPos(10, surface_desc->Height - 18 * 5);
text_helper.SetForegroundColor(FONT_COLOR);
text_helper.DrawTextLine(L"Controls (F1 to hide):");
text_helper.SetInsertionPos(40, surface_desc->Height - 18 * 4);
text_helper.DrawTextLine(L"Quit: ESC");
}
else
{
text_helper.SetInsertionPos(10, surface_desc->Height - 15 * 4);
text_helper.SetForegroundColor( D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f) );
text_helper.DrawTextLine(L"Press F1 for help");
}
text_helper.End();
}
//--------------------------------------------------------------------------------------
// Render the scene
//--------------------------------------------------------------------------------------
void CALLBACK OnFrameRender( IDirect3DDevice9* pd3dDevice, double fTime, float fElapsedTime, void* pUserContext )
{
HRESULT hr;
if(g_settings_dlg.IsActive())
{
g_settings_dlg.OnRender(fElapsedTime);
return;
}
float time = timeGetTime() / 1000.0f;
D3DXMATRIX mat_world;
D3DXMatrixRotationYawPitchRoll(&mat_world, time, time, time);
pd3dDevice->SetTransform(D3DTS_WORLD, &mat_world);
// Clear the render target and the zbuffer
V( pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_ARGB(0, 0, 0, 0), 1.0f, 0) );
// Render the scene
if( SUCCEEDED( pd3dDevice->BeginScene() ) )
{
for(DWORD i = 0; i < g_num_materials; i++)
{
pd3dDevice->SetMaterial(&g_mesh_materials[i]);
g_mesh->DrawSubset(i);
}
RenderText();
V(g_button_dlg.OnRender(fElapsedTime));
V( pd3dDevice->EndScene() );
}
}
//--------------------------------------------------------------------------------------
// Handle messages to the application
//--------------------------------------------------------------------------------------
LRESULT CALLBACK MsgProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam,
bool* pbNoFurtherProcessing, void* pUserContext )
{
*pbNoFurtherProcessing = g_dlg_resource_manager.MsgProc(hWnd, uMsg, wParam, lParam);
if(*pbNoFurtherProcessing)
return 0;
if(g_settings_dlg.IsActive())
{
g_settings_dlg.MsgProc(hWnd, uMsg, wParam, lParam);
return 0;
}
*pbNoFurtherProcessing = g_button_dlg.MsgProc(hWnd, uMsg, wParam, lParam);
if(*pbNoFurtherProcessing)
return 0;
return 0;
}
//--------------------------------------------------------------------------------------
// Handle keybaord event
//--------------------------------------------------------------------------------------
void CALLBACK OnKeyboardProc(UINT charater, bool is_key_down, bool is_alt_down, void* user_context)
{
if(is_key_down)
{
switch(charater)
{
case VK_F1:
g_show_help = !g_show_help;
break;
}
}
}
//--------------------------------------------------------------------------------------
// Handle events for controls
//--------------------------------------------------------------------------------------
void CALLBACK OnGUIEvent(UINT event, int control_id, CDXUTControl* control, void* user_context)
{
switch(control_id)
{
case IDC_TOGGLE_FULLSCREEN:
DXUTToggleFullScreen();
break;
case IDC_TOGGLE_REF:
DXUTToggleREF();
break;
case IDC_CHANGE_DEVICE:
g_settings_dlg.SetActive(true);
break;
}
}
//--------------------------------------------------------------------------------------
// Initialize dialogs
//--------------------------------------------------------------------------------------
void InitDialogs()
{
g_settings_dlg.Init(&g_dlg_resource_manager);
g_button_dlg.Init(&g_dlg_resource_manager);
g_button_dlg.SetCallback(OnGUIEvent);
int x = 35, y = 10, width = 125, height = 22;
g_button_dlg.AddButton(IDC_TOGGLE_FULLSCREEN, L"Toggle full screen", x, y, width, height);
g_button_dlg.AddButton(IDC_TOGGLE_REF, L"Toggle REF (F3)", x, y += 24, width, height);
g_button_dlg.AddButton(IDC_CHANGE_DEVICE, L"Change device (F2)", x, y += 24, width, height, VK_F2);
}
//--------------------------------------------------------------------------------------
// Initialize everything and go into a render loop
//--------------------------------------------------------------------------------------
INT WINAPI WinMain( HINSTANCE, HINSTANCE, LPSTR, int )
{
// Enable run-time memory check for debug builds.
#if defined(DEBUG) | defined(_DEBUG)
_CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
#endif
// Set the callback functions
DXUTSetCallbackDeviceCreated( OnCreateDevice );
DXUTSetCallbackDeviceReset( OnResetDevice );
DXUTSetCallbackDeviceLost( OnLostDevice );
DXUTSetCallbackDeviceDestroyed( OnDestroyDevice );
DXUTSetCallbackMsgProc( MsgProc );
DXUTSetCallbackFrameRender( OnFrameRender );
DXUTSetCallbackFrameMove( OnFrameMove );
DXUTSetCallbackKeyboard(OnKeyboardProc);
// TODO: Perform any application-level initialization here
InitDialogs();
// Initialize DXUT and create the desired Win32 window and Direct3D device for the application
DXUTInit( true, true, true ); // Parse the command line, handle the default hotkeys, and show msgboxes
DXUTSetCursorSettings( true, true ); // Show the cursor and clip it when in full screen
DXUTCreateWindow( L"Spherical Environment Mapping" );
DXUTCreateDevice( D3DADAPTER_DEFAULT, true, 640, 480, IsDeviceAcceptable, ModifyDeviceSettings );
// Start the render loop
DXUTMainLoop();
// TODO: Perform any application-level cleanup here
return DXUTGetExitCode();
}
下載示例工程