tutorial_05.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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      <td valign="top" width="100%">现在是后侧面。再次切换颜色。左下顶点又回到绿色，因为后侧面与右侧面共享这个角。</td>
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<pre>		glColor3f(1.0f,0.0f,0.0f);			<font color="#ffffaa">// 红色</font>
		glVertex3f( 0.0f, 1.0f, 0.0f);			<font color="#ffffaa">// 三角形的上顶点 (后侧面)</font>
		glColor3f(0.0f,1.0f,0.0f);			<font color="#ffffaa">// 绿色</font>
		glVertex3f( 1.0f,-1.0f, -1.0f);			<font color="#ffffaa">// 三角形的左下顶点 (后侧面)</font>
		glColor3f(0.0f,0.0f,1.0f);			<font color="#ffffaa">// 蓝色</font>
		glVertex3f(-1.0f,-1.0f, -1.0f);			<font color="#ffffaa">// 三角形的右下顶点 (后侧面)</font>
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      <td valign="top" width="100%">最后画左侧面。又要切换颜色。左下顶点是蓝色，与后侧面的右下顶点相同。右下顶点是蓝色，与前侧面的左下顶点相同。<br>
        到这里金字塔就画完了。因为金字塔只绕着Y轴旋转，我们永远都看不见底面，因而没有必要添加底面。如果您觉得有经验了，尝试增加底面(正方形)，并将金字塔绕X轴旋转来看看您是否作对了。确保底面四个顶点的颜色与侧面的颜色相匹配。</td>
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<pre>		glColor3f(1.0f,0.0f,0.0f);			<font color="#ffffaa">// 红色</font>
		glVertex3f( 0.0f, 1.0f, 0.0f);			<font color="#ffffaa">// 三角形的上顶点 (左侧面)</font>
		glColor3f(0.0f,0.0f,1.0f);			<font color="#ffffaa">// 蓝色</font>
		glVertex3f(-1.0f,-1.0f,-1.0f);			<font color="#ffffaa">// 三角形的左下顶点 (左侧面)</font>
		glColor3f(0.0f,1.0f,0.0f);			<font color="#ffffaa">// 绿色</font>
		glVertex3f(-1.0f,-1.0f, 1.0f);			<font color="#ffffaa">// 三角形的右下顶点 (左侧面)</font>
	glEnd();						<font color="#ffffaa">// 金字塔绘制结束</font>
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      <td valign="top" width="100%">接
下来开始画立方体。他由六个四边形组成。所有的四边形都以逆时针次序绘制。就是说先画右上角，然后左上角、左下角、最后右下角。您也许认为画立方体的背面
的时候这个次序看起来好像顺时针，但别忘了我们从立方体的背后看背面的时候，与您现在所想的正好相反。(译者注：您是从立方体的外面来观察立方体的)。<br>
        注意到这次我们将立方体移地更远离屏幕了。因为立方体的大小要比金字塔大，同样移入6个单位时，立方体看起来要大的多。这是透视的缘故。越远的对象看起来越小 
        :) 。</td>
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<pre>	glLoadIdentity();
	glTranslatef(1.5f,0.0f,-7.0f);				<font color="#ffffaa">// 先右移再移入屏幕</font>

	glRotatef(rquad,1.0f,1.0f,1.0f);			<font color="#ffffaa">// 在XYZ轴上旋转立方体</font>

	glBegin(GL_QUADS);					<font color="#ffffaa">// 开始绘制立方体</font>
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      <td valign="top" width="100%">先画立方体的顶面。从中心上移一单位，注意Y坐标始终为一单位，表示这个四边形与Z轴平行。先画右上顶点，向右一单位，再屏幕向里一单位。然后左上顶点，向左一单位，再屏幕向里一单位。然后是靠近观察者的左下和右下顶点。就是屏幕往外一单位。</td>
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<pre>		glColor3f(0.0f,1.0f,0.0f);			<font color="#ffffaa">// 颜色改为蓝色</font>
		glVertex3f( 1.0f, 1.0f,-1.0f);			<font color="#ffffaa">// 四边形的右上顶点 (顶面)</font>
		glVertex3f(-1.0f, 1.0f,-1.0f);			<font color="#ffffaa">// 四边形的左上顶点 (顶面)</font>
		glVertex3f(-1.0f, 1.0f, 1.0f);			<font color="#ffffaa">// 四边形的左下顶点 (顶面)</font>
		glVertex3f( 1.0f, 1.0f, 1.0f);			<font color="#ffffaa">// 四边形的右下顶点 (顶面)</font>
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      <td valign="top" width="100%">底面的画法和顶面十分类似。只是Y坐标变成了－1。如果我们从立方体的下面来看立方体的话，您会注意到右上角离观察者最近，因此我们先画离观察者最近的顶点。然后是左上顶点最后才是屏幕里面的左下和右下顶点。
        <p>如果您真的不在乎绘制多边形的次序(顺时针或者逆时针)的话，您可以直接拷贝顶面的代码，将Y坐标从1改成 -1，也能够工作。但一旦您进入象纹理映射这样的领域时，忽略绘制次序会导致十分怪异的结果。</p></td>
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</font><pre><font color="#aaffaa" size="3">		glColor3f(1.0f,0.5f,0.0f);			<font color="#ffffaa">// 颜色改成橙色</font>
		glVertex3f( 1.0f,-1.0f, 1.0f);			<font color="#ffffaa">// 四边形的右上顶点(底面)</font>
		glVertex3f(-1.0f,-1.0f, 1.0f);			<font color="#ffffaa">// 四边形的左上顶点(底面)</font>
		glVertex3f(-1.0f,-1.0f,-1.0f);			<font color="#ffffaa">// 四边形的左下顶点(底面)</font>
		glVertex3f( 1.0f,-1.0f,-1.0f);			<font color="#ffffaa">// 四边形的右下顶点(底面)</font>
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      <td valign="top" width="100%">接着画立方体的前面。保持Z坐标为一单位，前面正对着我们。</td>
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