D3D中的粒子系统(6)

2016/06/20 13:41
阅读数 20

14.3.3 例子程序:粒子枪

本例程实现了一个粒子枪系统,运行效果如图14.4所示:

下面是粒子枪系统的定义:
    class cParticleGun : public cParticleSystem
    {
    private:
        cCamera* m_camera;
    public:
        cParticleGun(cCamera* camera);
        virtual void reset_particle(sParticleAttribute* attr);
        virtual void update(float time_delta);
    };

构造函数需要提供一个照相机的位置点,这是因为系统需要知道照相机的位置及朝向,以决定在哪创建一个粒子。
    cParticleGun::cParticleGun(cCamera* camera)
    {
        m_camera        = camera;
        m_size            = 0.8f;
        m_vb_num        = 2048;
        m_vb_offset        = 0;
        m_vb_batch_num    = 512;
    }

reset_particle方法设置粒子的位置为当前照相机的位置,并且设置粒子运动的速度为照像机方向的100倍。这样,子弹将射向我们正在看的方向,粒子颜色为绿色。
    void cParticleGun::reset_particle(sParticleAttribute* attr)
    {
        attr->is_alive = true;
        D3DXVECTOR3 camera_dir;   
        m_camera->get_look(&camera_dir);
        attr->position      = m_camera->m_pos;    // change to camera position
            attr->position.y -= 1.0f;                // sightly below camera so it looks like we're carrying a gun
        // travels in the direction the camera is looking
            attr->velocity = camera_dir * 100.0f;
        attr->color        = D3DXCOLOR(0.0f, 1.0f, 0.0f, 1.0f);    // green
        attr->age        = 0.0f;
        attr->life_time = 1.0f;    // lives for 1 seconds
    }

update方法更新粒子的位置,并且杀死超过其生命周期的粒子,然后,我们搜索粒子列表删除已经死了的粒子。
    void cParticleGun::update(float time_delta)
    {
        for(list<sParticleAttribute>::iterator iter = m_particles.begin(); iter != m_particles.end(); iter++)
        {
            iter->position += iter->velocity * time_delta;
            iter->age       += time_delta;
            if(iter->age > iter->life_time)   
                iter->is_alive = false;    // kill
        }
        remove_dead_particles();
    }

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_gun;
    cCamera                g_camera(AIR_CRAFT);
        ////////////////////////////////////////////////////////////////////////////////////////////////////
    bool setup()
    {   
        srand((unsigned int)time(NULL));
        // create laser
        g_gun = new cParticleGun(&g_camera);
        g_gun->init(g_device, "flare_alpha.dds");
        // 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_gun;
        // pass NULL for the first parameter to instruct cleanup
        draw_basic_scene(NULL, 1.0f);
    }
        ///////////////////////////////////////////////////////////////////////////////////////////////////////
    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_gun->update(time_delta);
        // 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_gun->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);
            // Note: we use the message system over GetAsyncKeyState because GetAsyncKeyState was adding
            // particles too fast.  The message system is slower and does not add them as fast. 
            // This isn't the best solution, but works for illustration purposes.
            if(word_param == VK_SPACE)
                g_gun->add_particle();
            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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