tutorial_19.htm

如果你相信它就好好学学吧,同样这里也只是个入门

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面代码初始化每个粒子.我们从活跃的粒子开始.如果粒子不活跃,它在荧屏上将不出现,无论它有多少life.当我们使粒子活跃之後,我们给它life.我
怀疑给粒子生命和颜色渐变的是否是最好的方法,但当它运行一次后,效果很好!life满值是1.0f.这也给粒子完整的光亮.<br></td>
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</font><pre><font color="#aaffaa" size="3">	for (loop=0;loop&lt;MAX_PARTICLES;loop++)				<font color="#ffffaa">//初始化所有的粒子</font>
	{
		particle[loop].active=true;					<font color="#ffffaa">// 使所有的粒子为激活状态</font>
		particle[loop].life=1.0f;					<font color="#ffffaa">// 所有的粒子生命值为最大</font>
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    <td valign="top" width="100%"> 我们通过给定的值来设定粒子退色快慢.每次粒子被拉的时候life随着fade而减小.结束的数值将是0~99中的任意一个,然后平分1000份来得到一个很小的浮点数.最后我们把结果加上0.003f来使fade速度值不为0<br></td>
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<pre>		particle[loop].fade=float(rand()%100)/1000.0f+0.003f;		<font color="#ffffaa">// 随机生成衰减速率</font>
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既然粒子是活跃的,而且我们又给它生命,下面将给它颜色数值.一开始,我们就想每个粒子有不同的颜色.我怎么做才能使每个粒子与前面颜色箱里的颜色一一对
应那?数学很简单,我们用loop变量乘以箱子中颜色的数目与粒子最大值(MAX_PARTICLES)的余数.这样防止最后的颜色数值大于最大的颜色数
值(12).举例:900*(12/900)=12.1000*(12/1000)=12,等等<br></td>
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<pre>		particle[loop].r=colors[loop*(12/MAX_PARTICLES)][0];		<font color="#ffffaa">// 粒子的红色颜色</font>
		particle[loop].g=colors[loop*(12/MAX_PARTICLES)][1];		<font color="#ffffaa">// 粒子的绿色颜色</font>
		particle[loop].b=colors[loop*(12/MAX_PARTICLES)][2];		<font color="#ffffaa">// 粒子的蓝色颜色</font>
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    <td valign="top" width="100%">现在设定每个粒子移动的方向和速度.我们通过将结果乘于10.0f来创造开始时的爆炸效果.我们将会以任意一个正或负值结束.这个数值将以任意速度,任意方向移动粒子.</td>
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<pre>		particle[loop].xi=float((rand()%50)-26.0f)*10.0f;		<font color="#ffffaa">// 随机生成X轴方向速度</font>
		particle[loop].yi=float((rand()%50)-25.0f)*10.0f;		<font color="#ffffaa">// 随机生成Y轴方向速度</font>
		particle[loop].zi=float((rand()%50)-25.0f)*10.0f;		<font color="#ffffaa">// 随机生成Z轴方向速度</font>
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后,我们设定加速度的数值.不像一般的加速度仅仅把事物拉下,我们的加速度能拉出,拉下,拉左,拉右,拉前和拉后粒子.开始我们需要强大的向下加速度.为
了达到这样的效果我们将xg设为0.0f.在x方向没有拉力.我们设yg为-0.8f来产生一个向下的拉力.如果值为正则拉向上.我们不希望粒子拉近或远
离我们,所以将zg设为0.0f<br></td>
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<pre>		particle[loop].xg=0.0f;						<font color="#ffffaa">// 设置X轴方向加速度为0</font>
		particle[loop].yg=-0.8f;					<font color="#ffffaa">	//  设置Y轴方向加速度为-0.8</font>
		particle[loop].zg=0.0f;						<font color="#ffffaa">//  设置Z轴方向加速度为0</font>
	}
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在为有趣的部分.下面的部分是我们从哪里拉粒子,检查加速度等等.你要明白它是怎么实现的,因此仔细的看:)我们重置Modelview巨阵.在画粒子位
置的时候用glVertex3f()命令来代替tranlations,这样在我们画粒子的时候不会改变modelview巨阵 <br></td>
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<pre>int DrawGLScene(GLvoid)								<font color="#ffffaa">// 绘制粒子</font>
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);				<font color="#ffffaa">// 以黑色背景清楚</font>
	glLoadIdentity();								<font color="#ffffaa">// 重置模型变换矩阵</font>
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    <td valign="top" width="100%">我们开始创建一个循环loop.这个环将会更新每一个粒子. </td>
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<pre>	for (loop=0;loop&lt;MAX_PARTICLES;loop++)					<font color="#ffffaa">// 循环所有的粒子</font>
	{
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    <td valign="top" width="100%">首先我们做的事物是检查粒子是否活跃.如果不活跃,则不被更新.在这个程序中,它们始终活跃.但是在你自己的程序中,你可能想要使某粒子不活跃 
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<pre>		if (particle[loop].active)					<font color="#ffffaa">// 如果粒子为激活的</font>
		{
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