% DIPOLEDEMO  compute and display monopole and dipole mapping of visual field
%
%   DIPOLEDEMO builds a matrix of visual field positions in polar coordinates,
%   assembles a triangular mesh using these positions as vertices, then computes
%   transformations from the visual field to cortical coordinates via both the
%   monopole and dipole mappings (see Ref.s [1-3]). DIPOLEDEMO also visualizes
%   the two transformations by plotting the visual field mesh followed by the
%   mesh under the monopole mapping and the mesh under the dipole mapping.
%
%   DIPOLEDEMO(K, A, B) computes the monopole and dipole mappings using the
%   global mapping parameters K, A, and B, rather than the default parameters of
%   K=15, A=0.5, and B=80.
%
%   DIPOLEDEMO(K, A, B, ECC, NECC, NPOL) constructs the triangular mesh used for
%   the visual field, then monopole mapping, and the dipole mapping such that
%   the extent of the visual field is ECC degrees, and such that the mesh
%   vertices are laid out along NECC steps along eccentricity and NPOL steps
%   along polar angle, rather than with the default parameters of ECC=90,
%   NECC=20, and NPOL=22.
%  
%   [MESH, Z, W_MONOPOLE, W_DIPOLE] = DIPOLEDEMO(...) returns in MESH the matrix
%   representation of the triangular mesh used in the visualization as the data
%   structure produced by MATLAB's DELAUNAY function, i.e., MESH is a N-by-3
%   matrix such that each row contains indices either into the (complex)
%   coordinate vector Z for the visual field, W_MONOPOLE for the cortical
%   coordinates under the monopole mapping, or W_DIPOLE for the cortical
%   coordinates under the dipole mapping, where N is the number of triangles.
%
%   (This code produces plots identical to those appearing in Figure 1(a-c)
%   of Ref. [1].)
%
%  See also DELAUNAY, TRIPLOT.
%
%
%  References:
%  ===========
% 
% [1] Mukund Balasubramanian, Jonathan Polimeni, and Eric L. Schwartz. The
%     V1-V2-V3 complex: quasiconformal dipole maps in primate striate and
%     extra-striate cortex. Neural Networks, 15(10):1157-1163, 2002.
%
% [2] Eric L. Schwartz. Computational studies of the spatial architecture of
%     primate visual cortex: Columns, maps, and protomaps. In Alan Peters and
%     Kathleen Rockland, editors, Primary Visual Cortex in Primates, volume 10
%     of Cerebral Cortex. Plenum Press, March 1994.
%
% [3] Eric L. Schwartz. Anatomical and physiological correlates of visual
%     computation from striate to infero-temporal cortex. IEEE Transactions on
%     Systems, Man and Cybernetics, 14(2):257-271, March-April 1984.