源碼及素材下載大爆炸，煙霧痕跡甚至魔術(shù)飛彈尾部發(fā)出的微小火花，都是粒子(particle)所制造出來(lái)的特殊效果。在適當(dāng)?shù)臅r(shí)機(jī)，啟用alpha混合并繪制粒子，這樣粒子就能朝向觀察點(diǎn)（使用公告板），得到的結(jié)果就是混合對(duì)象的抽象拼貼，他們可以用于創(chuàng)建一些奇妙的效果。
粒子奇妙的地方就在于粒子的大小實(shí)際上是任意的，原因在于可以創(chuàng)建一個(gè)縮放矩陣，使其同粒子多邊形的世界變換矩陣結(jié)合起來(lái)。也就是說(shuō)，除非粒子紋理不同，否則只需要使用一個(gè)多邊形來(lái)繪制所有的粒子，無(wú)論如何，多邊形的數(shù)目都必須同紋理的數(shù)目保持一致。
還需要?jiǎng)?chuàng)建粒子圖像，圖像中心為一個(gè)實(shí)心（不透明）圓形，向圖像的邊緣延伸，圖像逐漸變透明，如下圖所示：
接著，需要設(shè)置4個(gè)頂點(diǎn)，這4個(gè)頂點(diǎn)使用了2個(gè)多邊形（可以使用三角形帶進(jìn)行優(yōu)化）。頂點(diǎn)的坐標(biāo)表示粒子的缺省大小，稍后需要將粒子進(jìn)行縮放，以適合這個(gè)大小。每個(gè)粒子都可以擁有獨(dú)特的屬性，包括粒子顏色（通過(guò)使用材質(zhì)來(lái)實(shí)現(xiàn)）。
接下來(lái)，將這個(gè)結(jié)構(gòu)體同一個(gè)含有兩個(gè)多邊形（創(chuàng)建一個(gè)正方形）的頂點(diǎn)緩沖結(jié)合起來(lái)，以便將多邊形渲染到3D設(shè)備上。在被繪制出來(lái)之前，每個(gè)粒子都需要通過(guò)它自己的世界矩陣進(jìn)行定向（當(dāng)然使用公告板）。然后將世界變換矩陣同每個(gè)粒子的縮放變換矩陣組合起來(lái)，再設(shè)置一個(gè)材質(zhì)（使用 IDirect3DDevice::SetMaterial函數(shù)），用來(lái)改變粒子的顏色。最后，繪制粒子。
完整源碼如下所示：
/***************************************************************************************
PURPOSE:
Particle Demo
Required libraries:
WINMM.lib, D3D9.LIB, D3DX9.LIB.
***************************************************************************************/
#include <windows.h>
#include <stdio.h>
#include "d3d9.h"
#include "d3dx9.h"
#pragma comment(lib, "winmm.lib")
#pragma comment(lib, "d3d9.lib")
#pragma comment(lib, "d3dx9.lib")
#pragma warning(disable : 4305 4244)
#define WINDOW_WIDTH 400
#define WINDOW_HEIGHT 400
#define Safe_Release(p) if((p)) (p)->Release();
// window handles, class and caption text.
HWND g_hwnd;
HINSTANCE g_inst;
static char g_class_name[] = "ParticleClass";
static char g_caption[] = "Particle Demo";
// the Direct3D and device object
IDirect3D9* g_d3d = NULL;
IDirect3DDevice9* g_d3d_device = NULL;
// the particle vertex buffer and texture
IDirect3DVertexBuffer9* g_particle_vb = NULL;
IDirect3DTexture9* g_particle_texture = NULL;
// The particle vertex format and descriptor
typedef struct
{
float x, y, z; // 3D coordinates
D3DCOLOR diffuse; // color
float u, v; // texture coordinates
} VERTEX;
#define VERTEX_FVF (D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX1)
// create a structure for tracking particles
struct PARTICLE
{
float x_pos, y_pos, z_pos; // coordinate
float x_add, y_add, z_add; // movement values
float red, green, blue; // colors
long timer, counter; // current and update counter
PARTICLE()
{
// position particle at origin
x_pos = y_pos = z_pos = 0.0;
// get a random update counter
counter = rand() % 50 + 10;
timer = 0;
// get a random speed
x_add = (float)(rand() % 11) - 5.0;
y_add = (float)(rand() % 11) - 5.0;
z_add = (float)(rand() % 11) - 5.0;
// get a random color
red = (float)(rand() % 101) / 100.0;
green = (float)(rand() % 101) / 100.0;
blue = (float)(rand() % 101) / 100.0;
}
};
PARTICLE* g_particles = NULL;
//--------------------------------------------------------------------------------
// Window procedure.
//--------------------------------------------------------------------------------
long WINAPI Window_Proc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return (long) DefWindowProc(hwnd, msg, wParam, lParam);
}
//--------------------------------------------------------------------------------
// Copy vertex data into vertex buffer, create texture from file.
//--------------------------------------------------------------------------------
BOOL Setup_Particles()
{
BYTE* vertex_ptr;
VERTEX verts[] = {
{ -50.0f, 50.0f, 0.0f, 0xFFFFFFFF, 0.0f, 0.0f },
{ 50.0f, 50.0f, 0.0f, 0xFFFFFFFF, 1.0f, 0.0f },
{ -50.0f, 0.0f, 0.0f, 0xFFFFFFFF, 0.0f, 1.0f },
{ 50.0f, 0.0f, 0.0f, 0xFFFFFFFF, 1.0f, 1.0f }
};
// create vertex buffers and stuff in data
if(FAILED(g_d3d_device->CreateVertexBuffer(sizeof(verts), 0, VERTEX_FVF, D3DPOOL_DEFAULT, &g_particle_vb, NULL)))
return FALSE;
// locks a range of vertex data and obtains a pointer to the vertex buffer memory
if(FAILED(g_particle_vb->Lock(0, 0, (void**)&vertex_ptr, 0)))
return FALSE;
memcpy(vertex_ptr, verts, sizeof(verts));
// unlocks vertex data
g_particle_vb->Unlock();
// get textures
D3DXCreateTextureFromFile(g_d3d_device, "Particle.bmp", &g_particle_texture);
// create some particles
g_particles = new PARTICLE[512];
return TRUE;
}
//--------------------------------------------------------------------------------
// Initialize d3d, d3d device, vertex buffer, texutre; set render state for d3d;
// set perspective matrix.
//--------------------------------------------------------------------------------
BOOL Do_Init()
{
D3DPRESENT_PARAMETERS present_param;
D3DDISPLAYMODE display_mode;
D3DXMATRIX mat_proj, mat_view;
// do a windowed mode initialization of Direct3D
if((g_d3d = Direct3DCreate9(D3D_SDK_VERSION)) == NULL)
return FALSE;
// retrieves the current display mode of the adapter
if(FAILED(g_d3d->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &display_mode)))
return FALSE;
ZeroMemory(&present_param, sizeof(present_param));
// initialize d3d presentation parameter
present_param.Windowed = TRUE;
present_param.SwapEffect = D3DSWAPEFFECT_DISCARD;
present_param.BackBufferFormat = display_mode.Format;
present_param.EnableAutoDepthStencil = TRUE;
present_param.AutoDepthStencilFormat = D3DFMT_D16;
// creates a device to represent the display adapter
if(FAILED(g_d3d->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, g_hwnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, &present_param, &g_d3d_device)))
return FALSE;
// set render state
// enable d3d lighting
g_d3d_device->SetRenderState(D3DRS_LIGHTING, TRUE);
// enable z-buffer
g_d3d_device->SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);
// set ambient light to highest level (to see particles)
g_d3d_device->SetRenderState(D3DRS_AMBIENT, 0xFFFFFFFF);
// create and set the projection matrix
// builds a left-handed perspective projection matrix based on a field of view
D3DXMatrixPerspectiveFovLH(&mat_proj, D3DX_PI/4.0, 1.0, 1.0, 1000.0);
// sets a single device transformation-related state
g_d3d_device->SetTransform(D3DTS_PROJECTION, &mat_proj);
// create and set the view transformation
D3DXMatrixLookAtLH(&mat_view, &D3DXVECTOR3(0.0f, 0.0f, -500.0f), &D3DXVECTOR3(0.0f, 0.0f, 0.0f),
&D3DXVECTOR3(0.0f, 1.0f, 0.0f));
g_d3d_device->SetTransform(D3DTS_VIEW, &mat_view);
// create the meshes
Setup_Particles();
return TRUE;
}
//--------------------------------------------------------------------------------
// Release all d3d resource.
//--------------------------------------------------------------------------------
BOOL Do_Shutdown()
{
delete[] g_particles;
Safe_Release(g_particle_vb);
Safe_Release(g_particle_texture);
Safe_Release(g_d3d_device);
Safe_Release(g_d3d);
return TRUE;
}
//--------------------------------------------------------------------------------
// Render a frame.
//--------------------------------------------------------------------------------
BOOL Do_Frame()
{
D3DXMATRIX mat_view, mat_world, mat_transposed, mat_transform;
static D3DMATERIAL9 s_material;
static BOOL s_is_mat_init = TRUE;
static DWORD s_counter = timeGetTime();
// limit to 30fps
if(timeGetTime() < s_counter+33)
return TRUE;
s_counter = timeGetTime();
// configure the material if first time called
if(s_is_mat_init = TRUE)
{
s_is_mat_init = FALSE;
ZeroMemory(&s_material, sizeof(s_material));
s_material.Diffuse.a = s_material.Ambient.a = 0.5f;
}
// clear device back buffer
g_d3d_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_RGBA(0, 64, 128, 255), 1.0f, 0);
// Begin scene
if(SUCCEEDED(g_d3d_device->BeginScene()))
{
// set the particle source, shader, texture.
g_d3d_device->SetStreamSource(0, g_particle_vb, 0, sizeof(VERTEX));
g_d3d_device->SetFVF(VERTEX_FVF);
g_d3d_device->SetTexture(0, g_particle_texture);
// get and set the transposed view matrix (billboard technique)
g_d3d_device->GetTransform(D3DTS_VIEW, &mat_view);
D3DXMatrixTranspose(&mat_transposed, &mat_view);
// enable alpha blending
g_d3d_device->SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
g_d3d_device->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_d3d_device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ONE);
// loop through all particles and draw them
for(short i = 0; i < 512; i++)
{
// move particle first
g_particles[i].x_pos += g_particles[i].x_add;
g_particles[i].y_pos += g_particles[i].y_add;
g_particles[i].z_pos += g_particles[i].z_add;
// reverse movements if past counter
if((g_particles[i].timer += 1) >= g_particles[i].counter)
{
g_particles[i].timer = 0;
g_particles[i].x_add *= -1.0f;
g_particles[i].y_add *= -1.0f;
g_particles[i].z_add *= -1.0f;
}
// setup the particle's world transformation
D3DXMatrixTranslation(&mat_transform, g_particles[i].x_pos, g_particles[i].y_pos, g_particles[i].z_pos);
D3DXMatrixMultiply(&mat_world, &mat_transform, &mat_transposed);
g_d3d_device->SetTransform(D3DTS_WORLD, &mat_world);
// set the particle's material
s_material.Diffuse.r = s_material.Ambient.r = g_particles[i].red;
s_material.Diffuse.g = s_material.Ambient.g = g_particles[i].green;
s_material.Diffuse.b = s_material.Ambient.b = g_particles[i].blue;
// Sets the material properties for the device
g_d3d_device->SetMaterial(&s_material);
// draw the particle
g_d3d_device->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, 2);
}
// release texture
g_d3d_device->SetTexture(0, NULL);
// end the scene
g_d3d_device->EndScene();
}
// present the contents of the next buffer in the sequence of back buffers owned by the device
g_d3d_device->Present(NULL, NULL, NULL, NULL);
return TRUE;
}
//--------------------------------------------------------------------------------
// Main function, routine entry.
//--------------------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR cmd_line, int cmd_show)
{
WNDCLASSEX win_class;
MSG msg;
g_inst = inst;
// create window class and register it
win_class.cbSize = sizeof(win_class);
win_class.style = CS_CLASSDC;
win_class.lpfnWndProc = Window_Proc;
win_class.cbClsExtra = 0;
win_class.cbWndExtra = 0;
win_class.hInstance = inst;
win_class.hIcon = LoadIcon(NULL, IDI_APPLICATION);
win_class.hCursor = LoadCursor(NULL, IDC_ARROW);
win_class.hbrBackground = NULL;
win_class.lpszMenuName = NULL;
win_class.lpszClassName = g_class_name;
win_class.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if(! RegisterClassEx(&win_class))
return FALSE;
// create the main window
g_hwnd = CreateWindow(g_class_name, g_caption, WS_CAPTION | WS_SYSMENU, 0, 0,
WINDOW_WIDTH, WINDOW_HEIGHT, NULL, NULL, inst, NULL);
if(g_hwnd == NULL)
return FALSE;
ShowWindow(g_hwnd, SW_NORMAL);
UpdateWindow(g_hwnd);
// initialize game
if(Do_Init() == FALSE)
return FALSE;
// start message pump, waiting for signal to quit.
ZeroMemory(&msg, sizeof(MSG));
while(msg.message != WM_QUIT)
{
if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
// draw a frame
if(Do_Frame() == FALSE)
break;
}
// run shutdown function
Do_Shutdown();
UnregisterClass(g_class_name, inst);
return (int) msg.wParam;
}
效果圖:
