基于范圍霧化的示例程序
要使用基于范圍的霧化，首先需要檢查當前硬件是否支持基于范圍的霧化：
// check if hardware supports range fog
D3DCAPS9 caps;
g_device->GetDeviceCaps(&caps);
if(! (caps.RasterCaps & D3DPRASTERCAPS_FOGRANGE))
return false;
在設置霧的顏色時，可將霧的顏色和背景顏色設置為一致，這樣遠處的物體看起來就像逐漸融入到背景中，視覺效果比較逼真。
霧化參數中，霧的開始距離和結束距離只對線性霧化有效，霧的濃度只對指數霧化和指數平方霧化有效。
無論頂點霧化還是像素霧化，在程序中必須設置合適的投影變換矩陣確保霧化效果正確，這在為那些不使用頂點坐標變換和光照流水線的程序中添加霧化效果造成了一定的困難，不過這種情況不多。
為了比較基于范圍的霧化和不基于范圍的霧化效果的不同，可以按下"R"鍵在基于范圍的霧化和不基于范圍的霧化之間進行切換。
源程序：
#include <d3dx9.h>
#pragma warning(disable : 4127)
#define CLASS_NAME "GameApp"
#define release_com(p) do { if(p) { (p)->Release(); (p) = NULL; } } while(0)
IDirect3D9* g_d3d;
IDirect3DDevice9* g_device;
ID3DXMesh* g_mesh;
D3DMATERIAL9* g_mesh_materials;
IDirect3DTexture9** g_mesh_textures;
DWORD g_num_materials;
struct sVertex
{
float x, y, z;
float u, v;
};
inline float height_field(float x, float z)
{
float y = 0.0f;
y += 10.0f * cosf(0.051f * x) * sinf(0.055f * x);
y += 10.0f * cosf(0.053f * z) * sinf(0.057f * z);
y += 2.0f * cosf(0.101f * x) * sinf(0.105f * x);
y += 2.0f * cosf(0.103f * z) * sinf(0.107f * z);
y += 2.0f * cosf(0.251f * x) * sinf(0.255f * x);
y += 2.0f * cosf(0.253f * z) * sinf(0.257f * z);
return y;
}
void setup_matrices()
{
// setup world matrix
D3DXMATRIX mat_world;
D3DXMatrixIdentity(&mat_world);
g_device->SetTransform(D3DTS_WORLD, &mat_world);
// setup view matrix
D3DXVECTOR3 eye(0.0f, 30.0f, -100.0f);
D3DXVECTOR3 at(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);
D3DXMATRIX mat_view;
D3DXMatrixLookAtLH(&mat_view, &eye, &at, &up);
g_device->SetTransform(D3DTS_VIEW, &mat_view);
// setup projection matrix
D3DXMATRIX mat_proj;
D3DXMatrixPerspectiveFovLH(&mat_proj, D3DX_PI/4, 1.0f, 1.0f, 500.0f);
g_device->SetTransform(D3DTS_PROJECTION, &mat_proj);
}
bool init_geometry()
{
ID3DXBuffer* material_buffer;
/*
D3DXLoadMeshFromXA(
LPCSTR pFilename,
DWORD Options,
LPDIRECT3DDEVICE9 pD3DDevice,
LPD3DXBUFFER *ppAdjacency,
LPD3DXBUFFER *ppMaterials,
LPD3DXBUFFER *ppEffectInstances,
DWORD *pNumMaterials,
LPD3DXMESH *ppMesh);
*/
if(FAILED(D3DXLoadMeshFromX("seafloor.x", D3DXMESH_SYSTEMMEM, g_device, NULL, &material_buffer, NULL,
&g_num_materials, &g_mesh)))
{
MessageBox(NULL, "Could not find seafloor.x", "ERROR", MB_OK);
return false;
}
D3DXMATERIAL* xmaterials = (D3DXMATERIAL*) material_buffer->GetBufferPointer();
g_mesh_materials = new D3DMATERIAL9[g_num_materials];
g_mesh_textures = new IDirect3DTexture9*[g_num_materials];
for(DWORD i = 0; i < g_num_materials; i++)
{
g_mesh_materials[i] = xmaterials[i].MatD3D;
// set ambient reflected coefficient, because .x file do not set it.
g_mesh_materials[i].Ambient = g_mesh_materials[i].Diffuse;
g_mesh_textures[i] = NULL;
if(xmaterials[i].pTextureFilename != NULL && strlen(xmaterials[i].pTextureFilename) > 0)
D3DXCreateTextureFromFile(g_device, xmaterials[i].pTextureFilename, &g_mesh_textures[i]);
}
material_buffer->Release();
// change model's height
IDirect3DVertexBuffer9* vertex_buffer;
g_mesh->GetVertexBuffer(&vertex_buffer);
sVertex* vertices;
vertex_buffer->Lock(0, 0, (void**)&vertices, 0);
DWORD num_vertices = g_mesh->GetNumVertices();
for(DWORD i = 0; i < num_vertices; i++)
vertices[i].y = height_field(vertices[i].x, vertices[i].z);
vertex_buffer->Unlock();
vertex_buffer->Release();
return true;
}
bool init_d3d(HWND hwnd)
{
g_d3d = Direct3DCreate9(D3D_SDK_VERSION);
if(g_d3d == NULL)
return false;
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
d3dpp.EnableAutoDepthStencil = TRUE;
d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
if(FAILED(g_d3d->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp, &g_device)))
{
return false;
}
// check if hardware supports range fog
D3DCAPS9 caps;
g_device->GetDeviceCaps(&caps);
if(! (caps.RasterCaps & D3DPRASTERCAPS_FOGRANGE))
return false;
if(! init_geometry())
return false;
setup_matrices();
g_device->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
g_device->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_SELECTARG1);
g_device->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_device->SetRenderState(D3DRS_RANGEFOGENABLE, TRUE);
g_device->SetRenderState(D3DRS_FOGCOLOR, 0xFF101010);
g_device->SetRenderState(D3DRS_AMBIENT, 0xFF00BB55);
return true;
}
void cleanup()
{
delete[] g_mesh_materials;
if(g_mesh_textures)
{
for(DWORD i = 0; i < g_num_materials; i++)
release_com(g_mesh_textures[i]);
delete[] g_mesh_textures;
}
release_com(g_mesh);
release_com(g_device);
release_com(g_d3d);
}
void render()
{
g_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_XRGB(5, 5, 5), 1.0f, 0);
g_device->BeginScene();
for(DWORD i = 0; i < g_num_materials; i++)
{
g_device->SetMaterial(&g_mesh_materials[i]);
g_device->SetTexture(0, g_mesh_textures[i]);
g_mesh->DrawSubset(i);
}
g_device->EndScene();
g_device->Present(NULL, NULL, NULL, NULL);
}
LRESULT WINAPI WinProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static float fog_start = 50;
static float fog_end = 200;
static float fog_density = 0.01f;
static bool use_range_fog = true;
switch(msg)
{
case WM_KEYDOWN:
switch(wParam)
{
case 48: // press key "0", disable fog.
g_device->SetRenderState(D3DRS_FOGENABLE, FALSE);
break;
case 49: // press key "1", enable linear fog.
g_device->SetRenderState(D3DRS_FOGENABLE, TRUE);
g_device->SetRenderState(D3DRS_FOGVERTEXMODE, D3DFOG_LINEAR);
g_device->SetRenderState(D3DRS_FOGSTART, *(DWORD*)&fog_start);
g_device->SetRenderState(D3DRS_FOGEND, *(DWORD*)&fog_end);
break;
case 50: // press key "2", enable exp fog.
g_device->SetRenderState(D3DRS_FOGENABLE, TRUE);
g_device->SetRenderState(D3DRS_FOGVERTEXMODE, D3DFOG_EXP);
g_device->SetRenderState(D3DRS_FOGDENSITY, *(DWORD*)&fog_density);
break;
case 51: // press key "3", enable exp2 fog.
g_device->SetRenderState(D3DRS_FOGENABLE, TRUE);
g_device->SetRenderState(D3DRS_FOGVERTEXMODE, D3DFOG_EXP2);
g_device->SetRenderState(D3DRS_FOGDENSITY, *(DWORD*)&fog_density);
break;
case 65 + 'R' - 'A':
use_range_fog = !use_range_fog;
g_device->SetRenderState(D3DRS_RANGEFOGENABLE, use_range_fog);
break;
case VK_ESCAPE:
DestroyWindow(hwnd);
break;
}
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR, INT)
{
WNDCLASSEX wc;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_CLASSDC;
wc.lpfnWndProc = WinProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = inst;
wc.hIcon = NULL;
wc.hCursor = NULL;
wc.hbrBackground = NULL;
wc.lpszMenuName = NULL;
wc.lpszClassName = CLASS_NAME;
wc.hIconSm = NULL;
if(! RegisterClassEx(&wc))
return -1;
HWND hwnd = CreateWindow(CLASS_NAME, "Direct3D App", WS_OVERLAPPEDWINDOW, 200, 100, 640, 480,
NULL, NULL, wc.hInstance, NULL);
if(hwnd == NULL)
return -1;
if(init_d3d(hwnd))
{
ShowWindow(hwnd, SW_SHOWDEFAULT);
UpdateWindow(hwnd);
MSG msg;
ZeroMemory(&msg, sizeof(msg));
while(msg.message != WM_QUIT)
{
if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
render();
Sleep(10);
}
}
cleanup();
UnregisterClass(CLASS_NAME, wc.hInstance);
return 0;
}
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