使用Direct3D创建凸凹贴图
在Direct3D中创建凸凹纹理贴图是非常简单的过程。使用D3DX函数D3DXComputeNormalMap()即可将Direct3D支持的所有图像格式转换成凸凹贴图。使用Direct3D函数计算法线贴图的最大优势就是在使用这些图片时，不需要知道图的生成方式。同样，还可以使用另一个D3DX函数D3DXSaveTextureToFile()，将新生成的凸凹贴图保存到文件中。
D3DXComputeNormalMap()函数原型非常简单，参数pTexture是保存法线贴图的Direct3D纹理对象。参数pSrcTexture是想要转换成法线贴图的原始图像。参数pSrcPalette是原始资源纹理的调色板，参数Flag可以是表4.1中的任何值，参数Channel可以是表4.2中的任何值，参数Amplitude是Normal Map的增加值或减少值。读者也许不需要使用这些调色板，但至少要知道这些选项可供选择。程序清单4.19给出了D3DXComputeNormalMap()函数的原型。
程序清单4.19 D3DXComputeNormalMap()函数原型
表4.1 D3DXComputeNormalMap()函数可用作标识符的参数值表
| D3DX_NORMAL_MIRROR_U | |
| D3DX_NORMAL_MIRROR_V | |
| D3DX_NORMAL_MIRROR | |
| D3DX_NORMAL_INVERTSIGN | |
| D3DX_NORMAL_COMPUTE_OCCLUSION |
表4.2 D3DXComputeNormalMap()函数的Channel参数值列表
| D3DX_CHANNEL_RED | 计算法线贴图时使用红色通道 |
| D3DX_CHANNEL_GREEN | 计算法线贴图时使用绿色通道 |
| D3DX_CHANNEL_BLUE | 计算法线贴图时使用蓝色通道 |
| D3DX_CHANNEL_ALPHA | 计算法线贴图时使用alpha通道 |
| D3DX_CHANNEL_LUMINANCE | 计算法线贴图时使用红色、绿色和蓝色通道的亮度值 |
在该函数的结尾处，参数pTexture存储新建的法线贴图。像所有其他Direct3D纹理一样，这里在使用完该对象时，必须将其释放。
#include<d3d9.h>
#include<d3dx9.h>
#define WINDOW_CLASS "UGPDX"
#define WINDOW_NAME "Creating D3D Normal Maps"
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
// Function Prototypes...
bool InitializeD3D(HWND hWnd, bool fullscreen);
bool InitializeObjects();
void RenderScene();
void Shutdown();
// Direct3D object and device.
LPDIRECT3D9 g_D3D = NULL;
LPDIRECT3DDEVICE9 g_D3DDevice = NULL;
// Matrices.
D3DXMATRIX g_projection;
D3DXMATRIX g_ViewMatrix;
// Vertex buffer to hold the geometry.
LPDIRECT3DVERTEXBUFFER9 g_VertexBuffer = NULL;
// Holds a texture image.
LPDIRECT3DTEXTURE9 g_Texture = NULL, g_NormalMap = NULL;
// A structure for our custom vertex type
struct stD3DVertex
{
float x, y, z;
unsigned long color;
float tu, tv;
};
// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_VERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX1)
LRESULT WINAPI MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_DESTROY:
PostQuitMessage(0);
return 0;
break;
case WM_KEYUP:
if(wParam == VK_ESCAPE) PostQuitMessage(0);
break;
}
return DefWindowProc(hWnd, msg, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE hInst, HINSTANCE prevhInst, LPSTR cmdLine, int show)
{
// Register the window class
WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
WINDOW_CLASS, NULL };
RegisterClassEx(&wc);
// Create the application's window
HWND hWnd = CreateWindow(WINDOW_CLASS, WINDOW_NAME, WS_OVERLAPPEDWINDOW,
100, 100, WINDOW_WIDTH, WINDOW_HEIGHT,
GetDesktopWindow(), NULL, wc.hInstance, NULL);
// Initialize Direct3D
if(InitializeD3D(hWnd, false))
{
// Show the window
ShowWindow(hWnd, SW_SHOWDEFAULT);
UpdateWindow(hWnd);
// Enter the message loop
MSG msg;
ZeroMemory(&msg, sizeof(msg));
while(msg.message != WM_QUIT)
{
if(PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else
RenderScene();
}
}
// Release any and all resources.
Shutdown();
// Unregister our window.
UnregisterClass(WINDOW_CLASS, wc.hInstance);
return 0;
}
bool InitializeD3D(HWND hWnd, bool fullscreen)
{
D3DDISPLAYMODE displayMode;
// Create the D3D object.
g_D3D = Direct3DCreate9(D3D_SDK_VERSION);
if(g_D3D == NULL) return false;
// Get the desktop display mode.
if(FAILED(g_D3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &displayMode)))
return false;
// Set up the structure used to create the D3DDevice
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));
if(fullscreen)
{
d3dpp.Windowed = FALSE;
d3dpp.BackBufferWidth = WINDOW_WIDTH;
d3dpp.BackBufferHeight = WINDOW_HEIGHT;
}
else
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = displayMode.Format;
// Create the D3DDevice
if(FAILED(g_D3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, &d3dpp, &g_D3DDevice)))
{
return false;
}
// Initialize any objects we will be displaying.
if(!InitializeObjects()) return false;
return true;
}
bool InitializeObjects()
{
// Fill in our structure to draw an object.
// x, y, z, color, texture coords.
stD3DVertex objData[] =
{
{-0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 1.0f},
{0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 1.0f},
{0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 0.0f},
{0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 0.0f},
{-0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 0.0f},
{-0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 1.0f}
};
// Create the vertex buffer.
if(FAILED(g_D3DDevice->CreateVertexBuffer(sizeof(objData), 0,
D3DFVF_VERTEX, D3DPOOL_DEFAULT, &g_VertexBuffer, NULL))) return false;
// Fill the vertex buffer.
void *ptr;
if(FAILED(g_VertexBuffer->Lock(0, sizeof(objData), (void**)&ptr, 0))) return false;
memcpy(ptr, objData, sizeof(objData));
g_VertexBuffer->Unlock();
// Load the texture image from file.
if(D3DXCreateTextureFromFile(g_D3DDevice, "heightMap.tga", &g_Texture) != D3D_OK)
return false;
D3DSURFACE_DESC desc;
g_Texture->GetLevelDesc(0,&desc);
// Create normal map texture the size of the original.
if(D3DXCreateTexture(g_D3DDevice, desc.Width, desc.Height, 0, 0, D3DFMT_A8R8G8B8,
D3DPOOL_MANAGED, &g_NormalMap) != D3D_OK) return false;
// Compute the normal map.
if(D3DXComputeNormalMap(g_NormalMap, g_Texture, 0, D3DX_NORMALMAP_MIRROR,
D3DX_CHANNEL_GREEN, 10) != D3D_OK) return false;
// Set the image states to get a good quality image.
g_D3DDevice->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_D3DDevice->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
// Set default rendering states.
g_D3DDevice->SetRenderState(D3DRS_LIGHTING, FALSE);
g_D3DDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
// Set the projection matrix.
D3DXMatrixPerspectiveFovLH(&g_projection, 45.0f, WINDOW_WIDTH/WINDOW_HEIGHT,
0.1f, 1000.0f);
g_D3DDevice->SetTransform(D3DTS_PROJECTION, &g_projection);
// Define camera information.
D3DXVECTOR3 cameraPos(0.0f, 0.0f, -1.0f);
D3DXVECTOR3 lookAtPos(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 upDir(0.0f, 1.0f, 0.0f);
// Build view matrix.
D3DXMatrixLookAtLH(&g_ViewMatrix, &cameraPos, &lookAtPos, &upDir);
return true;
}
void RenderScene()
{
// Clear the backbuffer.
g_D3DDevice->Clear(0, NULL, D3DCLEAR_TARGET,
D3DCOLOR_XRGB(0,0,0), 1.0f, 0);
// Begin the scene. Start rendering.
g_D3DDevice->BeginScene();
// Apply the view (camera).
g_D3DDevice->SetTransform(D3DTS_VIEW, &g_ViewMatrix);
// Draw square.
g_D3DDevice->SetTexture(0, g_NormalMap);
g_D3DDevice->SetStreamSource(0, g_VertexBuffer,0, sizeof(stD3DVertex));
g_D3DDevice->SetFVF(D3DFVF_VERTEX);
g_D3DDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);
// End the scene. Stop rendering.
g_D3DDevice->EndScene();
// Display the scene.
g_D3DDevice->Present(NULL, NULL, NULL, NULL);
}
void Shutdown()
{
if(g_D3DDevice != NULL) g_D3DDevice->Release();
g_D3DDevice = NULL;
if(g_D3D != NULL) g_D3D->Release();
g_D3D = NULL;
if(g_VertexBuffer != NULL) g_VertexBuffer->Release();
g_VertexBuffer = NULL;
if(g_Texture != NULL) g_Texture->Release();
g_Texture = NULL;
if(g_NormalMap != NULL) g_NormalMap->Release();
g_NormalMap = NULL;
}
有两个Direct3D纹理对象：一个用于存储原始图像，另一个用于存储计算过的法线贴图。然后从文件中将原始纹理加载到g_Texture对象中。一旦加载完毕，就可以得到图像表面的说明，这样在创建法线贴图时可以了解图像的宽度和高度。为法线贴图创建完空的纹理对象后，调用D3DXComputeNormalMap()函数计算该对象，并将其存储在g_NormalMap对象中。在D3DXComputeNormalMap()函数中，将法线贴图纹理对象、原始纹理对象以及一个强度值发送给该函数。当谈到参数Channel时，要指明在计算法线贴图时想要使用的通道。通常，图像应该是灰度图像，如果使用的不是灰度图像而且如果在计算时想要指定使用的具体颜色成分，这实际上也不是什么问题。