double cameraPos[3] = {0, 0, -100};

double cameraRot[3] = {30, -30, 0};

void begin3d() {

  glEnable(GL_DEPTH_TEST);

  glEnable(GL_CULL_FACE);

  glEnable(GL_LIGHTING);

  glEnable(GL_LIGHT0);

  glEnable(GL_COLOR_MATERIAL);

  glMatrixMode(GL_PROJECTION);

  glPushMatrix();

  glLoadIdentity();

  gluPerspective(60.0, (double)windowGetWidth()/(double)windowGetHeight(), 0.1, 10000.0);

  const double mm[16] = {

    0, 0, 1, 0,

    1, 0, 0, 0,

    0, 1, 0, 0,

    0, 0, 0, 1 };

  glMatrixMode(GL_MODELVIEW);

  glPushMatrix();

  glLoadIdentity();

  glTranslated(cameraPos[0], cameraPos[1], cameraPos[2]);

  glRotated(cameraRot[0], 1, 0, 0);

  glRotated(cameraRot[1], 0, 1, 0);

  glRotated(cameraRot[2], 0, 0, 1);

  glMultMatrixd(mm);

  float dir[4] = { 1, 1, 1, 0 };

  float k = 1.f/sqrtf(dir[0]*dir[0] + dir[1]*dir[1] + dir[2]*dir[2]);

  dir[0] *= k; dir[1] *= k; dir[2] *= k;

  glLightfv(GL_LIGHT0, GL_POSITION, dir);

}

void end3d() {

  glPopMatrix();

  glMatrixMode(GL_PROJECTION);

  glPopMatrix();

  glMatrixMode(GL_MODELVIEW);

  glDisable(GL_DEPTH_TEST);

}

void cubeDraw(double s) {

  s *= 0.5;

  glBegin(GL_QUADS);

  glColor3d(1, 0, 0);

  glNormal3d(0, 0, -1);

  glVertex3d(-s, -s, -s);

  glVertex3d(-s,  s, -s);

  glVertex3d( s,  s, -s);

  glVertex3d( s, -s, -s);

  glNormal3d(0, 0, 1);

  glVertex3d(-s, -s,  s);

  glVertex3d( s, -s,  s);

  glVertex3d( s,  s,  s);

  glVertex3d(-s,  s,  s);

  glColor3d(0, 1, 0);

  glNormal3d(0, -1, 0);

  glVertex3d(-s, -s, -s);

  glVertex3d( s, -s, -s);

  glVertex3d( s, -s,  s);

  glVertex3d(-s, -s,  s);

  glNormal3d(0, 1, 0);

  glVertex3d(-s,  s, -s);

  glVertex3d(-s,  s,  s);

  glVertex3d( s,  s,  s);

  glVertex3d( s,  s, -s);

  glColor3d(0, 0, 1);

  glNormal3d(-1, 0, 0);

  glVertex3d(-s, -s, -s);

  glVertex3d(-s, -s,  s);

  glVertex3d(-s,  s,  s);

  glVertex3d(-s,  s, -s);

  glNormal3d(1, 0, 0);

  glVertex3d( s, -s, -s);

  glVertex3d( s,  s, -s);

  glVertex3d( s,  s,  s);

  glVertex3d( s, -s,  s);

  glEnd();

  glColor3d(1, 1, 1);

}