有一款例子特效软件叫做particle illution,在影视后期和游戏制作领域都可以用到,相信很多人都接触过,今天我们用SDL+OpenGL来实现例子效果。
确保你搞定了物理模拟的代码!
所谓的例子系统,就是同时控制一大堆类似的对象,这些对象可能是形体,可能是图片,有着不同的特征(寿命,速度,位置)。有了之前的基础,我们可以很轻易地搞定今天的东西。
首先是粒子的头文件,我直接写成结构体了,里面有一些基本的属性。
- /*****************************************************************************
- Copyright: 2012, ustc All rights reserved.
- contact:k283228391@126.com
- File name: particle.h
- Description:Partical in opengl.
- Author:Silang Quan
- Version: 1.0
- Date: 2012.12.20
- *****************************************************************************/
- #ifndef PARTICLE_H
- #define PARTICLE_H
- #include "vector3d.h"
- typedef struct
- {
- float r;
- float g;
- float b;
- float alpha;
- }Color;
- typedef struct
- {
- Vector3D position;
- Vector3D velocity;
- Vector3D acceleration;
- Color color;
- float age;
- float life;
- float size;
- }Particle;
- #endif // PARTICLE_H
接下来是粒子系统类(类名拼写错了*-*)
- /*****************************************************************************
- Copyright: 2012, ustc All rights reserved.
- contact:k283228391@126.com
- File name: particalsystem.h
- Description:Partical in opengl.
- Author:Silang Quan
- Version: 1.0
- Date: 2012.12.20
- *****************************************************************************/
- #ifndef PARTICALSYSTEM_H
- #define PARTICALSYSTEM_H
- #include <vector>
- #include <math.h>
- #include <time.h>
- #include <stdlib.h>
- #include <iostream>
- #include <GL/gl.h>
- #include <GL/glu.h>
- #include "particle.h"
- #define PI 3.1415926
- using namespace std;
- class ParticalSystem
- {
- public:
- ParticalSystem();
- ParticalSystem(int _count,float _gravity){ptlCount=_count;gravity=_gravity;};
- void init();
- void simulate(float dt);
- void aging(float dt);
- void applyGravity();
- void kinematics(float dt);
- void render();
- virtual ~ParticalSystem();
- protected:
- private:
- int ptlCount;
- float gravity;
- GLUquadricObj *mySphere;
- vector<Particle> particles;
- };
- #endif // PARTICALSYSTEM_H
init:做一些例子系统的初始化工作;
aging:计算粒子的年龄;
applyGravity:向粒子施加重力;
kinematics:这个单词的意思是运动学,所以就是负责管理粒子的加速,位移;
simulate:例子模拟的总负责函数;
render:渲染粒子;
然后来看函数是怎么实现的:
- /*****************************************************************************
- Copyright: 2012, ustc All rights reserved.
- contact:k283228391@126.com
- File name: particalsystem.Cpp
- Description:Partical in opengl.
- Author:Silang Quan
- Version: 1.0
- Date: 2012.12.22
- *****************************************************************************/
- #include "particalsystem.h"
- ParticalSystem::ParticalSystem()
- {
- //ctor
- }
- ParticalSystem::~ParticalSystem()
- {
- //dtor
- }
- void ParticalSystem::init()
- {
- int i;
- srand(unsigned(time(0)));
- Color colors[3]={{0,0,1,1},{1,0,1,1}};
- for(i=0;i<ptlCount;i++)
- {
- //theta =(rand()%361)/360.0* 2*PI;
- Particle tmp={Vector3D(0,0,0),Vector3D(((rand()%50)-26.0f),((rand()%50)-26.0f),((rand()%50)-26.0f)),Vector3D(0,0,0),colors[rand()%2],0.0f,0.5+0.05*(rand()%10),0.3f};
- particles.push_back(tmp);
- }
- mySphere=gluNewQuadric();
- }
- void ParticalSystem::simulate(float dt)
- {
- aging(dt);
- applyGravity();
- kinematics(dt);
- }
- void ParticalSystem::aging(float dt)
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- iter->age+=dt;
- if(iter->age>iter->life)
- {
- iter->position=Vector3D(0,0,0);
- iter->age=0.0;
- iter->velocity=Vector3D(((rand()%30)-15.0f),((rand()%30)-11.0f),((rand()%30)-15.0f));
- }
- }
- }
- void ParticalSystem::applyGravity()
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- iter->acceleration=Vector3D(0,gravity,0);
- }
- void ParticalSystem::kinematics(float dt)
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- iter->position = iter->position+iter->velocity*dt;
- iter->velocity = iter->velocity+iter->acceleration*dt;
- }
- }
- void ParticalSystem::render()
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- float alpha = 1 - iter->age / iter->life;//calculate the alpha value according to the age of particle.
- Vector3D tmp=iter->position;
- glColor4f(iter->color.r,iter->color.g,iter->color.b,alpha);
- glPushMatrix();
- glTranslatef(tmp.x,tmp.y,tmp.z);
- gluSphere(mySphere,iter->size, 32, 16);
- glPopMatrix();
- }
- }
首先要在initGL函数中添加两句话:
- glEnable(GL_BLEND);
- glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
接着初始化一个例子系统,并对例子进行初始化:
ParticalSystem ps;
int main( int argc, char* argv[] ){// Color depth in bits of our window.int flags= SDL_OPENGL|SDL_RESIZABLE;//Set the SDLinitSDL(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP,flags);//Set the OpenGLinitGL(SCREEN_WIDTH, SCREEN_HEIGHT ); ps=ParticalSystem(100,-15.0); ps.init();//main loopwhile(true){/* Process incoming events. */handleEvents( );ps.simulate(0.01);/* Draw the screen. */renderGL( );}return 0;}
然后是渲染函数:
- void renderGL()
- {
- // Clear the color and depth buffers.
- glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT );
- // We don't want to modify the projection matrix. */
- glMatrixMode( GL_MODELVIEW );
- glLoadIdentity( );
- // Move down the z-axis.
- glTranslatef(0.0f,0.0f,-35.0f);
- ps.render();
- SDL_GL_SwapBuffers( );
- }
效果还是不错的~下面我们来实现一些更棒的效果!
动态模糊的实现比较简单,主循环不再每次把整个画面清空,而是每帧画一个半透明的黑色长方形,就可以模拟动态模糊(motion blur)的效果。
将之前的
- // Clear the color and depth buffers.
- glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT );
- // Clear the depth buffers.
- glClear(GL_DEPTH_BUFFER_BIT );
- void ParticalSystem::render()
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- float alpha = 1 - iter->age / iter->life;
- Vector3D tmp=iter->position;
- glColor4f(iter->color.r,iter->color.g,iter->color.b,alpha);
- //glColor4f(1.0f, 1.0f, 1.0f, 0.1);
- glPushMatrix();
- glTranslatef(tmp.x,tmp.y,tmp.z);
- gluSphere(mySphere,iter->size, 32, 16);
- glPopMatrix();
- }
- //Motion blue
- glColor4f(0.0f,0.0f,0.0f,0.1);
- glBegin(GL_QUADS);
- glVertex3f(-20.0f , -20.0f , 20.0f );
- glVertex3f( 20.0f , -20.0f , 20.0f );
- glVertex3f( 20.0f , 20.0f , 20.0f );
- glVertex3f(-20.0f , 20.0f , 20.0f );
- glEnd();
- }
效果还不错!
碰撞检测之前也实现过,在粒子系统里面加检测函数就Ok了.
- void ParticalSystem::checkBump(float x1,float x2,float y1,float y2)
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- if (iter->position.x - iter->size < x1 || iter->position.x +iter->size > x2) iter->velocity.x = -iter->velocity.x;
- if (iter->position.y - iter->size < y1 || iter->position.y + iter->size > y2) iter->velocity.y = -iter->velocity.y;
- }
- }
这个其实是opengl之外的东西了。我们要用的是SDL的获取鼠标信息函数:SDL_GetMouseState(&posX, &posY);
作用就是获取当前鼠标的位置。
接下来还要做的一件事是写坐标变换函数。因为opengl的坐标个SDL窗口的坐标并不是重合的,我们要将鼠标的当前坐标映射到OpenGL的坐标上去。
- float posTransX(int posX)
- {
- return (posX-400)/20.0;
- }
- float posTransY(int posY)
- {
- return (400-posY)/20.0;
- }
坐后要修改一下粒子的simulate函数。当粒子死亡的时候,他的初始位置设置为鼠标当前的位置。
- void ParticalSystem::aging(float dt,float posX,float posY)
- {
- for(vector<Particle>::iterator iter=particles.begin();iter!=particles.end();iter++)
- {
- iter->age+=dt;
- if(iter->age>iter->life)
- {
- iter->position=Vector3D(posX,posY,0);
- iter->age=0.0;
- iter->velocity=Vector3D(((rand()%30)-15.0f),((rand()%30)-11.0f),((rand()%30)-15.0f));
- }
- }
- }
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