clear all
close all

% Problem domain, in meters.
X = 2;
Y = 2;
D = 0.05;

% Problem domain, in cells.
NX = X/D;
NY = Y/D;

V_last = zeros(NY+1,NX+1);
V_next = zeros(NY+1,NX+1);

V_last(20:22, 14:16) = 1;
V_last(20:22, 24:26) = -1;

ITERATIONS = 400;

for i=1:ITERATIONS
  % Compute next voltage.
  for iy=2:NY
    for ix=2:NX
      V_next(iy,ix) = 1/4* ( V_last(iy-1,ix) + V_last(iy+1,ix) + V_last(iy,ix-1) + V_last(iy,ix+1) );
    end
  end
  % Overwrite conductors with their impressed potentials.
  V_next(20:22, 14:16) = 1;
  V_next(20:22, 24:26) = -1;
  % Iterate.
  V_last = V_next;
end


x_axis = linspace(0,X, NX + 1);
y_axis = linspace(0,Y, NY + 1);
[x,y] = meshgrid(x_axis, y_axis);
[Ex,Ey] = gradient(-V_last,D,D);
contour(x,y,V_last,20);
hold on
quiver(x,y,Ex,Ey);
set(gcf,'Color',[1 1 1]);
xlabel ('x, meters');
ylabel ('y, meters');
title ('ECE 311 - HW 7, Problem 1. Two conductor case.');
hold off
axis equal;