Matlab Drawing Helper

drawAtLineIntersection.m

% Draws a point at the intersection of two lines
% L1 = V1 + s * W1
% L2 = V2 + t * W2
function drawAtLineIntersection(V1, W1, V2, W2)

  if isequal(V1, V2) && isequal(W1, W2)
    c = V1; % could be any point on the line
  else
    i = [W1, -W2] \ (V2 - V1);
    c = V1 + i(1) * W1;
  end
  plot(c(1), c(2), 'b*');
end

drawCircle.m

% Draws a circle with radius r at point p
function drawCircle(p, r)
  phi = linspace(0, 2 * pi, 1000);
  plot(p(1) + r * cos(phi), p(2) + r * sin(phi));
end

drawLine.m

% Draws a line between point p1 and p2
function drawLine(p1, p2)
  plot([p1(1), p2(1)], [p1(2), p2(2)]);
end

drawLine3.m

% Draws a line between point p1 and p2 in 3D
function drawLine3(p1, p2)
  plot3([p1(1), p2(1)], [p1(2), p2(2)], [p1(3), p2(3)]);
end

drawLineEndpoint.m

% Draws two circles which are connected by a line
function drawLineEndpoint(p1, p2, r1, r2)
  n = (p2 - p1) / norm(p2 - p1);
  drawCircle(p1, r1);
  hold on
  drawCircle(p2, r2);
  drawLine(p1 + n * r1, p2 - n * r2);
  hold off
end