vectorCross3d

VECTORCROSS3D Vector cross product faster than inbuilt MATLAB cross.

   C = vectorCross3d(A, B) 
   returns the cross product of the 3D vectors A and B, that is: 
       C = A x B
   A and B must be N-by-3 element vectors. If either A or B is a 1-by-3
   row vector, the result C will have the size of the other input and will
   be the  concatenation of each row's cross product. 

   Example
     v1 = [2 0 0];
     v2 = [0 3 0];
     vectorCross3d(v1, v2)
     ans =
         0   0   6


   Class support for inputs A,B:
      float: double, single

   See also DOT.

0001 function c = vectorCross3d(a,b)
0002 %VECTORCROSS3D Vector cross product faster than inbuilt MATLAB cross.
0003 %
0004 %   C = vectorCross3d(A, B)
0005 %   returns the cross product of the 3D vectors A and B, that is:
0006 %       C = A x B
0007 %   A and B must be N-by-3 element vectors. If either A or B is a 1-by-3
0008 %   row vector, the result C will have the size of the other input and will
0009 %   be the  concatenation of each row's cross product.
0010 %
0011 %   Example
0012 %     v1 = [2 0 0];
0013 %     v2 = [0 3 0];
0014 %     vectorCross3d(v1, v2)
0015 %     ans =
0016 %         0   0   6
0017 %
0018 %
0019 %   Class support for inputs A,B:
0020 %      float: double, single
0021 %
0022 %   See also DOT.
0023 
0024 %   Sven Holcombe
0025 
0026 % needed_colons = max([3, length(size(a)), length(size(b))]) - 3;
0027 % tmp_colon = {':'};
0028 % clnSet = tmp_colon(ones(1, needed_colons));
0029 %
0030 % c = bsxfun(@times, a(:,[2 3 1],clnSet{:}), b(:,[3 1 2],clnSet{:})) - ...
0031 %     bsxfun(@times, b(:,[2 3 1],clnSet{:}), a(:,[3 1 2],clnSet{:}));
0032 
0033 % deprecation warning
0034 warning('geom3d:deprecated', ...
0035     [mfilename ' is deprecated, use ''crossProduct3d'' instead']);
0036 
0037 sza = size(a);
0038 szb = size(b);
0039 
0040 % Initialise c to the size of a or b, whichever has more dimensions. If
0041 % they have the same dimensions, initialise to the larger of the two
0042 switch sign(numel(sza) - numel(szb))
0043     case 1
0044         c = zeros(sza);
0045     case -1
0046         c = zeros(szb);
0047     otherwise
0048         c = zeros(max(sza, szb));
0049 end
0050 
0051 c(:) =  bsxfun(@times, a(:,[2 3 1],:), b(:,[3 1 2],:)) - ...
0052         bsxfun(@times, b(:,[2 3 1],:), a(:,[3 1 2],:));