firework.htm
来自「电脑图学（Computer Graphics）是资料结构、演算法与数学的应用」· HTM 代码 · 共 165 行
HTM
165 行
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<link rel="stylesheet" href="css/stdlayout.css" type="text/css">
<link rel="stylesheet" href="css/print.css" type="text/css">
<meta content="text/html; charset=gb2312" http-equiv="content-type">
<title>烟火</title>
</head>
<body>
<h3><a href="http://caterpillar.onlyfun.net/GossipCN/index.html">From
Gossip@caterpillar</a></h3>
<h1><a href="ComputerGraphics.htm">Computer Graphics: 烟火</a></h1>
粒子系统的基本概念很简单，只要使用类别或结构来包装粒子的动作操作与状态即可，然而其困难处在于，如何拟真的模拟出粒子的动作，这就与物理、化学有所关联了，然而有时候是可以用一些小技俩来简化真实世界中的粒子动作，而在荧幕上又有相当的效果。<br>
<br>
烟火粒子可以如下包装： <br>
<div style="margin-left: 40px;"><span style="font-weight: bold; font-family: Courier New,Courier,monospace;">public class FireworkParticle { </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private boolean state; // 粒子是否存活 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private Point position; // 粒子的位置 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private double vx, vy; // 粒子的速度 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private int life; // 粒子的生命值 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private Color currentcolor; // 粒子的颜色 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> private int time; // 粒子存活至今的时间 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> public void resume() {} // 启始粒子 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> public boolean getState() {} // 取得粒子存活状态 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> public Point getPoint() {} // 取得位子位置 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> public Color getColor() {} // 取得粒子颜色 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;"> public void nextState() {} // 改变至下一状态 </span><br style="font-weight: bold; font-family: Courier New,Courier,monospace;">
<span style="font-weight: bold; font-family: Courier New,Courier,monospace;">}</span><br>
</div>
<br>
Java物件导向的特性特别适合用来包装粒子系统，将所有与粒子有关的操作也一并包装进去；如果是VB或C，就使用结构来包装粒子的属性。<br>
<br>
在模拟的部份，首先是爆炸的时候，粒子所得到的水平与垂直速度，可以遵守动量守恒来计算出每一个粒子所获得的速度，但这边实际上并没有这么作，简单的使用
乱数来模拟也可以达到不错的效果；烟火粒子在下落的时候，是受重力的影响，vy = vt + 9.8 *
t；而粒子的颜色部份，初始时使用乱数来决定RGB值，而在粒子生命进入倒数时，改变为红色，最后再改变为蓝色，以配合夜空的颜色，让粒子有燃烧殆尽的感
觉。<br>
<br>
在移动的方面，由于荧幕大小有限，所以让一个像素代表实际移动一公尺，以免粒子因重力加速度的影响，一下子就跑出荧幕外了。<br>
<br>
大部份的模拟是如此，其它的请自己看看 <a href="fireWork.html">实例</a>，目前还没有加上烟的效果。<br>
<ul>
<li> Firework.java
</li>
</ul>
<pre>package onlyfun.caterpillar.graphics.particle;<br> <br>import java.applet.*; <br>import java.awt.*;<br>import javax.swing.JApplet;<br> <br>public class Firework extends JApplet implements Runnable { <br> private final int Max = 200; <br> private FireworkParticle particles[]; // 烟火粒子 <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 FireworkParticle[Max]; // 建立粒子 <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 < Max; i++) <br> particles[i] = new FireworkParticle(); <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(0,0, <br> appletWidth, appletHeight); <br> <br> for(int i = 0; i < Max; i++) { <br> if(particles[i].getState()) { <br> color = particles[i].getColor(); <br> double x = <br> particles[i].getPoint().getX(); <br> double y = <br> particles[i].getPoint().getY(); <br> drawOffScreen.setColor(color); <br> drawOffScreen.fillOval(<br> (int)x, (int)y, 1, 1); <br> particles[i].nextState(); <br> } <br> } <br> <br> for(int i = 0; i < Max; i++) { <br> if(particles[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 < Max; i++) {<br> particles[i].resume(new Point(xCenter, <br> yCenter), Max);<br> particles[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>}<br> <br>class FireworkParticle { <br> private boolean state; // 粒子是否存活 <br> private Point position; // 粒子的位置 <br> private double vx, vy; // 粒子的速度 <br> private int life; // 粒子的生命值 <br> private Color currentcolor; // 粒子的颜色 <br> private int time; // 粒子存活至今的时间 <br> <br> public void resume(Point p, int random) { <br> position = p; <br> state = true; <br> vx = Math.random()*random - Math.random()*random; <br> vy = Math.random()*random - Math.random()*random; <br> currentcolor = <br> new Color((int)(Math.random()*255), <br> (int)(Math.random()*255), <br> (int)(Math.random()*255)); <br> time = 0; <br> } <br> <br> public void setLife(int life) {<br> this.life = life;<br> }<br> <br> public boolean getState() { <br> return state; <br> } <br> <br> public Point getPoint() { <br> return position; <br> } <br> <br> public Color getColor() { <br> return currentcolor; <br> } <br> <br> public void nextState() { <br> vy += 9.8*time;<br> position.setLocation(position.getX() + <br> vx * 0.1, position.getY() + vy * 0.1);<br> life--; <br> time++; <br> <br> if(life < 0) { <br> life = 0; <br> state = false; <br> } <br> else if(life < 2) { <br> currentcolor = new Color(0, 0, 255); <br> } <br> else if(life < 5){ <br> currentcolor = new Color(255, 0, 0); <br> } <br> } <br>} <br></pre>
<br>
<br>
<br>
</body>
</html>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?