📄 fireworksmoke.htm
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<title>烟火与烟</title>
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<h3><a href="http://caterpillar.onlyfun.net/GossipCN/index.html">From
Gossip@caterpillar</a></h3>
<h1><a href="ComputerGraphics.htm">Computer Graphics: 烟火与烟</a></h1>
事实上之前的烟火在施放时并没有烟，只有火花，可以结合两个粒子系统来制作烟火在燃烧过程中所产生的烟硝轨迹。<br>
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在结合两个粒子系统时，要注意，每个粒子都是独立的，火花粒子就是火花粒子，不会与烟粒子相互影响，只不过烟粒子产生的位置是火花的目前位置，只要将位置的资讯传递给烟粒子物件就可以了。<br>
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指定烟粒子的方式采用比较简单的方式，首先产生足够的烟粒子，它们的状态都为false，然后等待重新指定它们为复活状态，每次绘制完火花后，在一堆烟粒子物件中寻找状态为false的烟粒子，然后指定新的初始位置给这些粒子，如此烟粒子就会跟随着火花的轨迹而产生了。<br>
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这边需要之前制作的FireworkParticle与SmokeParticle类别，您可以直接看看 <a href="fireworkAndsmoke.html">范例</a>。<br>
<ul>
<li> FireworkAndSmoke.java </li>
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<pre>package onlyfun.caterpillar.graphics.particle;<br> <br>import java.awt.*;<br>import javax.swing.JApplet;<br><br>public class FireworkAndSmoke extends JApplet <br> implements Runnable { <br> private final int fireworkMax = 200; <br> private final int smokeMax = fireworkMax * 10;<br> private FireworkParticle fireworkParticles[]; // 烟火粒子<br> private SmokeParticle smokeParticles[]; // 烟粒子<br> private int appletWidth, appletHeight, xCenter,yCenter; <br> private Image offScreen; <br> private Graphics drawOffScreen; <br> <br> public void init() { <br> setBackground(Color.black); // 背景为黑色 <br><br> fireworkParticles = <br> new FireworkParticle[fireworkMax]; // 建立粒子<br> smokeParticles = new SmokeParticle[smokeMax];<br> <br> // 取得显像区域 <br> appletWidth = getSize().width; <br> appletHeight = getSize().height; <br> <br> // 烟火初始位置 <br> xCenter = appletWidth/2 + <br> (int)(Math.random()* 150 - 150); <br> yCenter = appletHeight/2 +<br> (int)(Math.random()* 150 - 150); <br> for(int i = 0; i < fireworkMax; i++) <br> fireworkParticles[i] = new FireworkParticle(); <br> <br> for(int i = 0; i < smokeMax; i++) {<br> smokeParticles[i] = new SmokeParticle();<br> }<br> <br> // 建立次画面 <br> offScreen = createImage(appletWidth, appletHeight); <br> drawOffScreen = offScreen.getGraphics(); <br> } <br> <br> public void start() { <br> (new Thread(this)).start(); <br> } <br> <br> public void update(Graphics g) { <br> paint(g); <br> } <br> <br> public void paint(Graphics g) { <br> g.drawImage(offScreen, 0, 0, this); <br> } <br> <br> public void run() { <br> Color color; <br> boolean replay; <br> <br> while(true) { <br> replay = true; <br> drawOffScreen.clearRect(<br> 0,0, appletWidth, appletHeight); <br> <br> for(int i = 0; i < fireworkMax; i++) { <br> if(fireworkParticles[i].getState()) { <br> color = fireworkParticles[i].getColor(); <br> double x = <br> fireworkParticles[i].getPoint().getX(); <br> double y = <br> fireworkParticles[i].getPoint().getY(); <br> drawOffScreen.setColor(color); <br> drawOffScreen.fillOval((int)x, (int)y, 1, 1); <br> <br> // 为烟火加上烟<br> for(int j = 0; j < smokeMax; j++) { <br> if(!smokeParticles[j].getState()) { <br> smokeParticles[j].setLife(<br> (int)(50*Math.random()));<br> smokeParticles[j].resume(<br> new Point((int)x, (int)y)); <br> break;<br> }<br> } <br> <br> fireworkParticles[i].nextState(); <br> } <br> } <br> <br> for(int j = 0; j < smokeMax; j++) { <br> if(smokeParticles[j].getState()) { <br> color = smokeParticles[j].getColor(); <br> double sx = <br> smokeParticles[j].getPoint().getX(); <br> double sy = <br> smokeParticles[j].getPoint().getY(); <br> drawOffScreen.setColor(color); <br> drawOffScreen.fillOval(<br> (int) sx, (int) sy, 2, 2); <br> smokeParticles[j].nextState(); <br> } <br> } <br> <br> for(int i = 0; i < fireworkMax; i++) { <br> if(fireworkParticles[i].getState()) { <br> replay = false; <br> break; <br> } <br> } <br> <br> // 是否重新施放 <br> if(replay) { <br> // 烟火初始位置 <br> xCenter = appletWidth/2 + <br> (int)(Math.random()* 150 - 150); <br> yCenter = appletHeight/2 + <br> (int)(Math.random()* 150 - 150); <br> <br> for(int i = 0; i < fireworkMax; i++) {<br> fireworkParticles[i].resume(<br> new Point(xCenter, yCenter), <br> fireworkMax);<br> fireworkParticles[i].setLife(<br> (int) (Math.random()*20));<br> }<br> } <br> <br> // 重绘画面 <br> repaint(); <br> <br> // 暂停执行绪 150 毫秒 <br> try { <br> Thread.sleep(150); <br> } <br> catch (InterruptedException e) { } <br> } <br> } <br>}</pre>
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