static float fog_color[] = {0.4,0.4,0.4,1.0};
float fogDensity=0.008;
glEnable(GL_FOG);
glFogi(GL_FOG_MODE, GL_EXP);
glFogf(GL_FOG_DENSITY, fogDensity);
glFogfv(GL_FOG_COLOR, fog_color);