📄 smokeparticle.htm
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<title>烟粒子</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: 烟粒子</a></h1>
粒子系统的制作理念都是相同的，难是难在物理或化学等模拟，烟粒子就是如此，轻飘飘的烟动向不定，受周遭的环境而影响运动，例如风吹，在这边是利用烟粒子重量当作风吹时的受动因子。<br>
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您可以先 看看 <a href="smoke.html">范例</a>。<br>
<ul>
<li> Smoke.java
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</ul>
<pre>package onlyfun.caterpillar.graphics.particle;<br><br>import java.awt.*; <br>import java.applet.*; <br>import javax.swing.JApplet;<br> <br>public class Smoke extends Applet implements Runnable { <br> private final int Max = 1000; <br> private SmokeParticle particles[]; // 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> particles = new SmokeParticle[Max]; // 建立粒子 <br> <br> // 取得显像区域 <br> appletWidth = getSize().width; <br> appletHeight = getSize().height; <br> <br> // 烟初始位置 <br> xCenter = appletWidth/2; <br> yCenter = 2*appletHeight/3; <br> for(int i=0; i<Max; i++) <br> particles[i] = new SmokeParticle();<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> <br> int windTime = 0;<br> double windX = 0;<br> while(true) { <br> drawOffScreen.clearRect(0,0,<br> appletWidth,appletHeight); <br> <br> if(windTime <=0) {<br> // 风速 x<br> windX = 30*Math.random()-15; <br> // 风吹时间<br> windTime = (int)(20*Math.random()); <br> }<br> <br> for(int i = 0; i < Max; i++) {<br> if(particles[i].getState()) {<br> color = particles[i].getColor();<br> <br> // 受风动的效果不一 <br> double wx =<br> windX/particles[i].getWeight();<br> double x = <br> particles[i].getPoint().getX();<br> double y = <br> particles[i].getPoint().getY();<br> particles[i].getPoint().setLocation(x+wx, y);<br><br> x = particles[i].getPoint().getX();<br> y = particles[i].getPoint().getY();<br><br> drawOffScreen.setColor(color); <br> drawOffScreen.fillOval(<br> (int) x, (int)y, 2, 2); <br> particles[i].nextState(); <br> } <br> } <br> <br> for(int i = 0; i < Max; i++) { <br> if(!particles[i].getState()) {<br> particles[i].setLife(<br> (int)(255*Math.random()));<br> particles[i].resume(new Point(<br> (int)(xCenter+ Math.random()*10), <br> (int)(yCenter + Math.random()*10))); <br> }<br> } <br> <br> // 重绘画面 <br> repaint(); <br> <br> try { <br> Thread.sleep(150); <br> } <br> catch (InterruptedException e) { } <br> <br> windTime--;<br> } <br> } <br>}<br> <br>class SmokeParticle { <br> private Point position; // 位置 <br> private double vx, vy; // 水平与垂直速度 <br> private double weight; // 重量 <br> private int life; // 生命周期 <br> private boolean state; // 状态 <br> private Color color; // 颜色 <br> <br> public void resume(Point p) { <br> position = p; <br> vx = 0; <br> vy = -1; <br> weight = 10* Math.random() + 1; <br> state = true; <br> color = new Color(life, life, life); <br> } <br><br> public void setLife(int life) {<br> this.life = life;<br> }<br> <br> public void setWeight(double weight) {<br> this.weight = weight;<br> }<br> <br> public Point getPoint() { <br> return position; <br> } <br> <br> public double getWeight() { <br> return weight; <br> } <br> <br> public Color getColor() { <br> return new Color(life, life, life); <br> } <br> <br> public boolean getState() { <br> return state; <br> } <br> <br> public void nextState() { <br> position.setLocation(position.getX(), <br> position.getY() + vy);<br> life -= 1; <br> <br> if(life <=0) { <br> life = 0; <br> state = false; <br> } <br> } <br>}</pre>
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