function [ct] = backProject(rays,phis,dim,fltr)

sz = size(rays)
ct = [];

for i = 1:dim(1)
  for j = 1:dim(2)
     superpositive = 0;
     for phi = 1:sz(1)
     dimensions = [length(rays{phi}) length(rays{phi})];
     ray = rays{phi};
     if(fltr==1)
       ray = conv(ray,RamLak(15));
       ray = crop1D(ray,dimensions(2));
     elseif(fltr==2)
       ray = conv(ray,SheppLogan(9));
       ray = crop1D(ray,dimensions(2));
     else
       ray = ray;
     end
     
     Po = [-dimensions(2)/2; -dimensions(1)/2];
       Pt = [dimensions(2)/2; -dimensions(1)/2];
       index = footDist([(j-1)-(dim(2)/2),(dim(1)-(i-1))-(dim(1)/2)],Po,Pt,phis(phi));
       %subIndex = floor(index);
       subIndex = max(1,min(dimensions(2),double(floor(index))));
       superIndex = min(dimensions(2),subIndex+1);
       %superIndex = subIndex+1;
       subDiff = norm(index-subIndex);
       superDiff = norm(index-superIndex);
       if(subDiff < superDiff)
         newValue = ray(subIndex);
       else
         newValue = ray(superIndex);
       end  
       superpositive = superpositive + newValue; 
     end
    ct(i,j)=superpositive;
   end
i
end