function       out=CPleastsqmethod();

% to read data from G.byt file %
infname='CalgridG.byt';
fid=fopen(infname);
G=fread(fid,'float');
fclose(fid);
%no of elements%
%n=G(1);
%A=reshape(G(2:141),7,20)';
A=read_calib_data(infname,18);
%reading the world coordinates%
xw=A(:,1);
yw=A(:,2);
zw=A(:,3);
%reading the camera coordinates%
xc=A(:,4)
yc=A(:,5)
%reading the projector coordinates%
xp=A(:,6);
yp=A(:,7)


%%%calculate transformation matrix using linear triangulation%%%

%%%perspective matrix for camera%%%%
N=18;
for i=1:N
    Ac(2*i-1,:)=[xw(i) yw(i) zw(i) 1 0 0 0 0 -xc(i)*xw(i) -xc(i)*yw(i) -xc(i)*zw(i)];
    Ac(2*i,:)=[0 0 0 0 xw(i) yw(i) zw(i) 1 -yc(i)*xw(i) -yc(i)*yw(i) -yc(i)*zw(i)];
    Pc(2*i-1,1)=xc(i);
    Pc(2*i,1)=yc(i);
end
mc=(inv(Ac'*Ac))*Ac'*Pc;
mc(12)=1;
mwc=(reshape(mc,4,3))';
%%%perspective matrix for projector%%%%

for i=1:N
   
    Ayp(i,:)=[xw(i) yw(i) zw(i) 1 -yp(i)*xw(i) -yp(i)*yw(i) -yp(i)*zw(i)];
    Pp(i,1)=yp(i);
end

mp=(inv(Ayp'*Ayp))*Ayp'*Pp;
mp(8)=1;
mwp=(reshape(mp,4,2))';

%%%%%reconstruct the 3D world co-ordinates%%%%%
M=18;
for i=1:M
c(1,1)=mwc(1,1)-mwc(3,1)*xc(i);
c(1,2)=mwc(1,2)-mwc(3,2)*xc(i); 
c(1,3)=mwc(1,3)-mwc(3,3)*xc(i);
c(2,1)=mwc(2,1)-mwc(3,1)*yc(i);
c(2,2)=mwc(2,2)-mwc(3,2)*yc(i);
c(2,3)=mwc(2,3)-mwc(3,3)*yc(i);
c(3,1)=mwp(1,1)-mwp(2,1)*yp(i);
c(3,2)=mwp(1,2)-mwp(2,2)*yp(i); 
c(3,3)=mwp(1,3)-mwp(2,3)*yp(i);
d(1,1)=xc(i)-mwc(1,4);
d(2,1)=yc(i)-mwc(2,4);
d(3,1)=yp(i)-mwp(1,4);
W(:,i)=inv(c)*d;
end

new_xw(:,1)=W(1,:);
new_yw(:,1)=W(2,:);
new_zw(:,1)=W(3,:);

pdisplay=zeros(18,3);
olddisplay=pdisplay;


pdisplay(:,1)=new_xw(:,1);
pdisplay(:,2)=new_yw(:,1);
pdisplay(:,3)=new_zw(:,1);

olddisplay(:,1)=xw;
olddisplay(:,2)=yw;
olddisplay(:,3)=zw;

pdisplay
olddisplay


errval(:,1)= xw-new_xw(:,1);
errval(:,2)= yw-new_yw(:,1);
errval(:,3)= zw-new_zw(:,1)
%
erval = sqrt(errval(:,1).^2+errval(:,2).^2+errval(:,3).^2)
meanerval=mean(erval)

%write the projector parameters
fp = fopen('proj.txt','w');
fprintf(fp,'%f ',mwp(1,1));fprintf(fp,'%f ',mwp(1,2));fprintf(fp,'%f ',mwp(1,3));fprintf(fp,'%f\n',mwp(1,4));
fprintf(fp,'%f ',mwp(2,1));fprintf(fp,'%f ',mwp(2,2));fprintf(fp,'%f ',mwp(2,3));fprintf(fp,'%f\n',mwp(2,4));
%fprintf(fp,'%f ',mwp(3,1));fprintf(fp,'%f ',mwp(3,2));fprintf(fp,'%f ',mwp(3,3));fprintf(fp,'%f\n',mwp(3,4));
fclose(fp);
%write the camera parameters
fp = fopen('cam.txt','w');
fprintf(fp,'%f ',mwc(1,1));fprintf(fp,'%f ',mwc(1,2));fprintf(fp,'%f ',mwc(1,3));fprintf(fp,'%f\n',mwc(1,4));
fprintf(fp,'%f ',mwc(2,1));fprintf(fp,'%f ',mwc(2,2));fprintf(fp,'%f ',mwc(2,3));fprintf(fp,'%f\n',mwc(2,4));
fprintf(fp,'%f ',mwc(3,1));fprintf(fp,'%f ',mwc(3,2));fprintf(fp,'%f ',mwc(3,3));fprintf(fp,'%f\n',mwc(3,4));
fclose(fp);
mwc
mwp
out=1;