利用OpenGL在窗口上绘制出三维坐标

/*今天刚开通CSDN博客，以此记录我的编程学习之旅*/

按时间顺序来讲，这是计算机图形学课程的第一个编程实践，大概是在一年前吧。这个程序是在nehe OpenGL框架下完成的，现在回头来看，这是一个很基础、很简单的小程序，但可以说是我编写（改编）的第一个图形窗口程序。

下面是程序绘制三维坐标的主体代码：

int DrawGLScene(GLvoid) // 这个自定义函数用于完成窗口场景绘制

{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// 清屏及深度缓存
glLoadIdentity();
// 重置模型观察矩阵
glTranslatef(-1.0f,-1.0f,-6.0f);
//平移绘制起点（向左平移1个单位，向下平移1个单位，朝垂直屏幕向内平移6个单位）
glColor3f(1.0f,0.0f,0.0f);
// 设置画笔颜色（RGB：此处为红色）

// 绘制x、y、z轴线段
glBegin(GL_LINES);

glVertex3f( 0.0f, 0.0f, 0.0f );
//绘制线段的起点，这里为相对坐标，即相将glTranslatef移动后的点作为原点
glVertex3f( 3.0f,0.0f, 0.0f  );
//确定第一条线段的终点（3，0，0）
glVertex3f( 0.0f,0.0f, 0.0f );
//确定第二条线段的起点（0，0，0）
glVertex3f( 0.0f,3.0f, 0.0f ); 
//确定第二条线段的终点（0，3，0）
glVertex3f( 0.0f,0.0f, 0.0f );
glVertex3f( 0.0f,0.0f, 3.0f );                   
glEnd();

//平移起点并重新设置画笔颜色用于区分绘制的物体
glTranslatef(-1.0f,-1.0f,-6.0f);
        glColor3f(0.5f,0.5f,1.0f);

//绘制一个矩形

glBegin(GL_QUADS);

glVertex3f(0.0f, 0.0f, 0.0f);
// Top Left
glVertex3f(0.0f, 3.0f, 0.0f);
// Top Right
glVertex3f(0.0f,3.0f, 3.0f);
// Bottom Right
glVertex3f(0.0f,0.0f, 3.0f);
// Bottom Left
glEnd();

//更改画笔颜色，并绘制另外一个矩形

   glColor3f(0.0f,0.0f,1.0f);
// Set The Color To Blue One Time Only
glBegin(GL_QUADS);
// Draw A Quad
glVertex3f(0.0f, 0.0f, 0.0f);
// Top Left
glVertex3f(3.0f, 0.0f, 0.0f);
// Top Right
glVertex3f(3.0f,0.0f, 3.0f);
// Bottom Right
glVertex3f(0.0f,0.0f, 3.0f);
// Bottom Left
glEnd();

//在窗口上显示“X”表示X轴
glTranslatef(4.0f,0.0f,0.0f);
glColor3f(0.0f,1.0f,0.0f);
glBegin(GL_LINES);

glVertex3f( 0.0f, 0.0f, 0.0f);

glVertex3f(1.0f,-1.0f, 0.0f);

glVertex3f( 1.0f,0.0f, 0.0f);
glVertex3f( 0.0f,-1.0f, 0.0f); 
glEnd(); 

//在窗口上显示“Y”表示Y轴
glTranslatef(-5.0f,4.0f,0.0f);
glColor3f(0.0f,0.5f,0.5f);
glBegin(GL_LINES);

glVertex3f( 0.0f, 0.0f, 0.0f);

glVertex3f(0.0f,-1.0f, 0.0f);
glVertex3f( 0.0f, 0.0f, 0.0f);
glVertex3f( -0.5f,0.5f, 0.0f);
glVertex3f( 0.0f, 0.0f, 0.0f);
glVertex3f( 0.5f,0.5f, 0.0f); 
glEnd(); 

//在窗口上显示“Z”表示Z轴
glTranslatef(0.0f,-4.0f,4.0f);
glColor3f(0.5f,0.0f,0.5f);
glBegin(GL_LINES);

glVertex3f( 0.0f, 0.0f, 0.0f);

glVertex3f(0.5f,0.0f, 0.0f);
        glVertex3f(0.5f,0.0f, 0.0f);               
glVertex3f( 0.0f,-0.5f, 0.0f);
glVertex3f( 0.0f,-0.5f, 0.0f);
glVertex3f( 0.5f,-0.5f, 0.0f); 
glEnd();                                       
return TRUE;

}

附上运行效果截图：

借此，在这里总结一下OpenGL生成点、线的函数实现吧：

（1）用OpenGL生成点（点的绘制）

glPointSize(2.0f);
//设置点的大小，这里设置为两个像素

glBegin(GL_POINTS);

glVertex2f(0.0,3.0);
//绘制二维点

glVertex3f(0.0f,0.0f,0,3f);
//绘制三维点

glEnd();

（2）绘制直线

glLineWidth(2.0f);
//设置直线的宽度为2个像素

glBegin(GL_LINES);

glVertex2f(0.0f,3.0f);
//第一条直线的起点

glVertex2f(0.0f,0.0f);
//第一条直线的终点

glEnd();

//可以利用glEnable(GL_LINE_STIPPLE);  glLineStipple(1,0x00FF);……glDisable(GL_LINE_STIPPLE);绘制自定义线形（此处为点划线）

（3）绘制折线

glBegin(GL_LINE_STRIP);

glVertex2f(-0.9f,1.0f);

glVertex2f(0.0f,0.0f);

glVertex2f(0.9f,0.5f);

glEnd();

//在glBegin()和glEnd()之间是折线的顶点，由这些顶点以此相连成折线，不会自动闭合