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14.3.2 例子程序：焰火系统
本例程实现了一个焰火例子系统，运行效果如图14.3所示：
火系统类定义如下：
class cFirework : public cParticleSystem
{
public:
cFirework(D3DXVECTOR3* origin, int num_particles);
virtual void reset_particle(sParticleAttribute* attr);
virtual void update(float time_delta);
virtual void pre_render();
};
构造函数需要提供一个点作为粒子系统中的原点，和系统中的粒子数，原点是火焰爆发的那个点。
cFirework::cFirework(D3DXVECTOR3* origin, int num_particles)
{
m_origin = *origin;
m_size = 0.9f;
m_vb_num = 2048;
m_vb_offset = 0;
m_vb_batch_num = 512;
for(int i = 0; i < num_particles; i++)
add_particle();
}
reset_particle方法在原点位置初始化粒子系统，并在边界球内创建一个随机的速度，粒子系统中的每个例子有一个随机的颜色，我们定义粒子只能存活2秒。
void cFirework::reset_particle(sParticleAttribute* attr)
{
attr->is_alive = true;
attr->position = m_origin;
D3DXVECTOR3 min = D3DXVECTOR3(-1.0f, -1.0f, -1.0f);
D3DXVECTOR3 max = D3DXVECTOR3(1.0f, 1.0f, 1.0f);
get_random_vector(&attr->velocity, &min, &max);
// normalize to make spherical
D3DXVec3Normalize(&attr->velocity, &attr->velocity);
attr->velocity *= 100.0f;
attr->color = D3DXCOLOR(get_random_float(0.0f, 1.0f),
get_random_float(0.0f, 1.0f),
get_random_float(0.0f, 1.0f),
1.0f);
attr->age = 0.0f;
attr->life_time = 2.0f; // lives for 2 seconds
}
update方法更新每个粒子的位置，并在粒子超出自己的生活周期时杀死它。注意：这个系统不移除死掉的粒子，这么做是因为我们想产生一个新的火焰的时候，我们只要简单的重新设置已经存在的死了的火焰系统就可以了。这样我们不必频繁的去产生和释放粒子。
void cFirework::update(float time_delta)
{
for(list<sParticleAttribute>::iterator iter = m_particles.begin(); iter != m_particles.end(); iter++)
{
// only update living particles
if(iter->is_alive)
{
iter->position += iter->velocity * time_delta;
iter->age += time_delta;
if(iter->age > iter->life_time) // kill
iter->is_alive = false;
}
}
}
重载pre_render
以使绘制粒子时与地板颜色融合。
void cFirework::pre_render()
{
cParticleSystem::pre_render();
m_device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ONE);
}
执行程序：
#include "d3dUtility.h"
#include "camera.h"
#include "ParticleSystem.h"
#include <cstdlib>
#include <ctime>
#pragma warning(disable : 4100)
const int WIDTH = 640;
const int HEIGHT = 480;
IDirect3DDevice9* g_device;
cParticleSystem* g_exploder;
cCamera g_camera(AIR_CRAFT);
////////////////////////////////////////////////////////////////////////////////////////////////////
bool setup()
{
srand((unsigned int)time(NULL));
// create firwworlk system
D3DXVECTOR3 origin(0.0f, 10.0f, 50.0f);
g_exploder = new cFirework(&origin, 6000);
g_exploder->init(g_device, "flare.bmp");
// setup a basic scnen, the scene will be created the first time this function is called.
draw_basic_scene(g_device, 1.0f);
// set the projection matrix
D3DXMATRIX proj;
D3DXMatrixPerspectiveFovLH(&proj, D3DX_PI/4.0f, (float)WIDTH/HEIGHT, 1.0f, 1000.0f);
g_device->SetTransform(D3DTS_PROJECTION, &proj);
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
void cleanup()
{
delete g_exploder;
// pass NULL for the first parameter to instruct cleanup
draw_basic_scene(NULL, 0.0f);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
bool display(float time_delta)
{
// update the camera
if( GetAsyncKeyState(VK_UP) & 0x8000f )
g_camera.walk(4.0f * time_delta);
if( GetAsyncKeyState(VK_DOWN) & 0x8000f )
g_camera.walk(-4.0f * time_delta);
if( GetAsyncKeyState(VK_LEFT) & 0x8000f )
g_camera.yaw(-1.0f * time_delta);
if( GetAsyncKeyState(VK_RIGHT) & 0x8000f )
g_camera.yaw(1.0f * time_delta);
if( GetAsyncKeyState('N') & 0x8000f )
g_camera.strafe(-4.0f * time_delta);
if( GetAsyncKeyState('M') & 0x8000f )
g_camera.strafe(4.0f * time_delta);
if( GetAsyncKeyState('W') & 0x8000f )
g_camera.pitch(1.0f * time_delta);
if( GetAsyncKeyState('S') & 0x8000f )
g_camera.pitch(-1.0f * time_delta);
// update the view matrix representing the camera's new position/orientation
D3DXMATRIX view_matrix;
g_camera.get_view_matrix(&view_matrix);
g_device->SetTransform(D3DTS_VIEW, &view_matrix);
g_exploder->update(time_delta);
if(g_exploder->is_dead())
g_exploder->reset();
// render now
g_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0x00000000, 1.0f, 0);
g_device->BeginScene();
D3DXMATRIX identity_matrix;
D3DXMatrixIdentity(&identity_matrix);
g_device->SetTransform(D3DTS_WORLD, &identity_matrix);
draw_basic_scene(g_device, 1.0f);
// order important, render firework last.
g_device->SetTransform(D3DTS_WORLD, &identity_matrix);
g_exploder->render();
g_device->EndScene();
g_device->Present(NULL, NULL, NULL, NULL);
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
LRESULT CALLBACK wnd_proc(HWND hwnd, UINT msg, WPARAM word_param, LPARAM long_param)
{
switch(msg)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
case WM_KEYDOWN:
if(word_param == VK_ESCAPE)
DestroyWindow(hwnd);
break;
}
return DefWindowProc(hwnd, msg, word_param, long_param);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, PSTR cmd_line, int cmd_show)
{
if(! init_d3d(inst, WIDTH, HEIGHT, true, D3DDEVTYPE_HAL, &g_device))
{
MessageBox(NULL, "init_d3d() - failed.", 0, MB_OK);
return 0;
}
if(! setup())
{
MessageBox(NULL, "Steup() - failed.", 0, MB_OK);
return 0;
}
enter_msg_loop(display);
cleanup();
g_device->Release();
return 0;
}
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