You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spm_mars_newSeg.m
    path of file: ./repos/fieldtrip/external/mars
    
    the code of the file until where you have to start completion: function cls = spm_mars_newSeg(res,tc,bf,df,mode,tcm)
% FORMAT cls = spm_mars_newSeg(res,tc,bf,df,mode,tcm)
%
% Write out the results from toolbox 'New Segment'. This function is only for
% the purpose of making toolbox 'MARS' backwards compatible with 'New Segment'.
    
function [x1,y1,z1] = defs(sol,z,MT,prm,x0,y0,z0,M)
iMT = inv(MT);
x1  = x0*iMT(1,1)+iMT(1,4);
y1  = y0*iMT(2,2)+iMT(2,4);
z1  = (z0(z)*iMT(3,3)+iMT(3,4))*ones(size(x1));
x1a = x0    + spm_bsplins(sol{1},x1,y1,z1,prm);
y1a = y0    + spm_bsplins(sol{2},x1,y1,z1,prm);
z1a = z0(z) + spm_bsplins(sol{3},x1,y1,z1,prm);
x1  = M(1,1)*x1a + M(1,2)*y1a + M(1,3)*z1a + M(1,4);
y1  = M(2,1)*x1a + M(2,2)*y1a + M(2,3)*z1a + M(2,4);
z1  = M(3,1)*x1a + M(3,2)*y1a + M(3,3)*z1a + M(3,4);
return;
%=======================================================================

%=======================================================================
function t = transf(B1,B2,B3,T)
if ~isempty(T)
    d2 = [size(T) 1];
    t1 = reshape(reshape(T, d2(1)*d2(2),d2(3))*B3', d2(1), d2(2));
    t  = B1*t1*B2';
else
    t = zeros(size(B1,1),size(B2,1),size(B3,1));
end