local2global.m

function glob = local2global(grid,einds,loc,params)
%function glob = local2global(grid,einds,loc,params)
% function performing a local to global coordinate change of
% vectors of coordinate pairs.
%
% If the first three vertices of a rectangle are 'v1,v2,v3', then the
% global coordinate of a single point is
% @code glob = v1 + loc(:,1).*(v2-v1) + loc(:,2).*(v3-v1); @endcode
%
% Parameters:
%  loc: matrix of size `K \times 2` holding local barycentric coordinate pairs
%       for each cell index `i_k`, `k=1,...,K`.
%  einds: vector of cell indices `i_k`, `k=1,...,K`.
%
% Return values:
%  glob: global coordinate pairs '[X, Y]' with vectors 'X' and 'Y'
%        of length `K`.
%

% Bernard Haasdonk 2.2.2009

% for triagrid:

loc3 = loc(1)-loc(2);
VI1 = grid.VI(einds,4);
VI2 = grid.VI(einds,1);
VI3 = grid.VI(einds,2);

X = grid.X(VI1)' + loc(1).* (grid.X(VI2)' - grid.X(VI1)');
Y = grid.Y(VI1)' + loc(2).* (grid.Y(VI3)' - grid.Y(VI1)');

glob = [X(:),Y(:)];