OpenGL使用雾坐标，找不到标识符？？？
我在编写红宝书《OpenGL编程指南（第六版）》上面的第六章使用雾坐标的程序时，出现错误，未声明的标识符和找不到标识符。是在搞不清楚是为什么了。求大侠指教！
另外，说一下我的机器是刚刚新买的，这是不是和版本有关系啊？那应该怎么改正呢？
源代码：
#include <GL/glut.h>#include <iostream>using namespace std;static GLfloat f1,f2,f3;static void init(){ GLfloat fogColor[4] = {0.0,0.25,0.25,1.0}; f1 = 1.0f; f2 = 5.0f; f3 = 10.0f; glEnable(GL_FOG); glFogi(GL_FOG_MODE,GL_EXP); glFogfv(GL_FOG_COLOR,fogColor); glFogf(GL_FOG_DENSITY,0.25); glHint(GL_FOG_HINT,GL_DONT_CARE); glFogi(GL_FOG_COORD_SRC,GL_FOG_COORD); glClearColor(0.0,0.25,0.25,1.0);}void display(){ glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0f,0.75f,0.0f); glBegin(GL_TRIANGLES); glFogCoordf(f1); glVertex3f(2.0f,-2.0f,0.0f); glFogCoordf(f2); glVertex3f(-2.0f,0.0f,-5.0f); glFogCoordf(f3); glVertex3f(0.0f,2.0f,-10.0f); glEnd(); glutSwapBuffers();}void keyboard(unsigned char key,int x,int y){ switch(key) { case 'c': glFogi(GL_FOG_COORD_SRC,GL_FRAGMENT_DEPTH); glutPostRedisplay(); break; case 'C': glFogi(GL_FOG_COORD_SRC,GL_FOG_COORD); glutPostRedisplay(); break; case '1': f1 += 0.25; glutPostRedisplay(); break; case '2': f2 += 0.25; glutPostRedisplay(); break; case '3': f3 += 0.25; glutPostRedisplay(); break; case '8': if(f1 > 0.25) { f1 -= 0.25; glutPostRedisplay(); break; } case '9': if(f2 > 0.25) { f2 -= 0.25; glutPostRedisplay(); } break; case '0': if(f3 > 0.25) { f3 -= 0.25; glutPostRedisplay(); } break; case 'b': glMatrixMode(GL_MODELVIEW); glTranslatef(0.0,0.0,-0.25); glutPostRedisplay(); break; case 'f': glMatrixMode(GL_MODELVIEW); glTranslatef(0.0,0.0,0.25); glutPostRedisplay(); break; case 27: exit(0); break; default: break; }}int main(int argc,char** argv){ glutInit(&argc,argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize(500,500); glutCreateWindow("Fog Coordinate"); init(); glutKeyboardFunc(keyboard); glutDisplayFunc(display); glutMainLoop(); return 0;}