void yrot(double theta){
  theta*=(pi / 180);
  double ct=Math.cos(theta);
  double st=Math.sin(theta);
  float Nxx=(float)(xx * ct + zx * st);
  float Nxy=(float)(xy * ct + zy * st);
  float Nxz=(float)(xz * ct + zz * st);
  float Nxo=(float)(xo * ct + zo * st);
  float Nzx=(float)(zx * ct - xx * st);
  float Nzy=(float)(zy * ct - xy * st);
  float Nzz=(float)(zz * ct - xz * st);
  float Nzo=(float)(zo * ct - xo * st);
  xo=Nxo;
  xx=Nxx;
  xy=Nxy;
  xz=Nxz;
  zo=Nzo;
  zx=Nzx;
  zy=Nzy;
  zz=Nzz;
}

void yrot ( double theta ) { theta *= ( pi / 180 ) ; double ct = Math . cos ( theta ) ; double st = Math . sin ( theta ) ; float Nxx = ( float ) ( xx * ct + zx * st ) ; float Nxy = ( float ) ( xy * ct + zy * st ) ; float Nxz = ( float ) ( xz * ct + zz * st ) ; float Nxo = ( float ) ( xo * ct + zo * st ) ; float Nzx = ( float ) ( zx * ct - xx * st ) ; float Nzy = ( float ) ( zy * ct - xy * st ) ; float Nzz = ( float ) ( zz * ct - xz * st ) ; float Nzo = ( float ) ( zo * ct - xo * st ) ; xo = Nxo ; xx = Nxx ; xy = Nxy ; xz = Nxz ; zo = Nzo ; zx = Nzx ; zy = Nzy ; zz = Nzz ; }
rotate theta degrees about the y axis
