OpenGL 绘制长方体 计算机图形学
不同面填充模式显示出不同的效果，如下面三幅截图：
上图通过glPolygonMode(GL_FRONT, GL_LINE);函数的调用，实现了显示前面面上的边线，而下面的面显示为默认的面填充，显示效果为如上图。
上图通过glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);函数的调用，实现了显示前后面面上的边线，显示效果就是图中的的只显示边线，而没有面填充效果。
上图通过glPolygonMode(GL_BACK, GL_LINE);函数的调用，实现了显示后面面上的边线，而下面的面显示为默认的面填充，显示效果为如上图。
【注】算法代码如下，其中void quad(GLint n1,GLint n2,GLint n3,GLint n4,GLint index)为画立方体的算法：
#include
#include
#ifdef __APPLE__
#include
#else
#include
#endif
#include
void init(void)
{
glClearColor(1.0,1.0,1.0,0.0);
glMatrixMode(GL_MODELVIEW);//设置当前矩阵模式为视图模型矩阵
glLoadIdentity();
//设置视点的位置，视线的方向和相机的向上方向
gluLookAt(0,0,0, 0,0,-1, 0,1,0); //该设置为默认设置
glScalef(0.3,1.0,0.5); //产生比例变换，分别设置物体在x，y，z方向上缩放因子，根据需要自己可以设置
glRotatef(45,1.0,1.0,1.0);//产生旋转变换，让物体绕（1，1，1）轴旋转45度
glMatrixMode(GL_PROJECTION);//设置当前矩阵模式为投影矩阵
glFrustum(-4,4,-4,4,0,20);////设置场景投影时的可视范围
}
float points[8][3] = {{0,0,0},{0,0.5,0},{0.5,0,0},{0.5,0.5,0},{0,0,0.5},{0,0.5,0.5},{0.5,0,0.5},{0.5,0.5,0.5}};
float colors[6][3] = {{0.25,0,0},{0.25,0.25,0.25},{0,0,0.25},{0.5,0.25,0},{0,0.25,0.25},{0.25,0,0.25}};
void vertexArray(void)
{
glClear(GL_COLOR_BUFFER_BIT);
// glColor 3f(1.0,1.0,0.0);
//glPolygonMode(GL_FRONT, GL_LINE);// 设置多边形的显示模式为面填充模式，该设置也是默认设置
glFrontFace(GL_CCW); //设置前面的面的模式为逆时针模式， 该设置也是默认设置
//glShadeModel(GL_SHADE_MODEL);// 默认就是此参数，可忽略，为了明确说明特意指定
void quad(GLint n1,GLint n2,GLint n3,GLint n4,GLint index);
quad(6,2,3,7,1);
quad(5,1,0,4,2);
quad(7,3,1,5,3);
quad(4,0,2,6,4);
quad(2,0,1,3,5);
quad(7,5,4,6,6);
glFlush();
}
void quad(GLint n1,GLint n2,GLint n3,GLint n4,GLint index)
{
glColor3f(0.0,1.0,0.0);
glEnable(GL_POLYGON_OFFSET_FILL);
glPolygonOffset(1.0,1.0);
glDisable(GL_POLYGON_OFFSET_FILL);
glColor3f(colors[index][0],colors[index][1],colors[index][2]);
//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
//glPolygonMode(GL_FRONT, GL_LINE);
glPolygonMode(GL_BACK, GL_LINE);
//glColor3f(1.0,1.0,0);
glBegin(GL_QUADS);
glVertex3fv(points[n1]);
glVertex3fv(points[n2]);
glVertex3fv(points[n3]);
glVertex3fv(points[n4]);
glEnd();
}
int main (int argc, char** argv)
{
glutInit (&argc, argv); // Initialize GLUT.
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode.
glutInitWindowPosition (50, 100); // Set top-left display-window position.
glutInitWindowSize (600, 500); // Set display-window width and height.
glutCreateWindow ("An Example OpenGL Program"); // Create display window.
init(); // Execute initialization procedure.
glutDisplayFunc (vertexArray); // Send graphics to display window.
glutMainLoop ( );// Send graphics to display window. // Display everything and wait.
return 0;
}