Illusion

%% Optical Illusion

% Script to make simple optical illusion using polygon set operations.

%% Calculate the polygon points

% This polygon is made by intersection of two circles. Then the resulting polygon is

% translated and scaled.Two different colors are chosen to color the boundary. Half of the % boundary of polygon will colored with black and remaining half with white.

num_points = 100;

t = 0 : 2*pi/num_points : 2*pi;

x = sin(t);

y = cos(t);

[x, y] = polybool('intersection', x, y+1, x+1, y);

x = (x-0.5)*0.65;

y = (y-0.5)*0.65;

len_x = length(x);

num1 = floor(len_x/2);

num2 = len_x - num1;

[theta,r] = cart2pol(x,y);

colmap = [zeros(num1,3) ; ones(num2,3)]; %colormap for edges

num_row = 20; %number of rows

num_col = 20; %number of column

%% Draw the polygons

% Two loops ,one for row and other for column.In each iteration of inner loop the polygon

% is rotated by a small angle. Outer loop gives a rotation which is constant for one

% iteration of inner loop.

k = 2*0.1*pi;

for i = 1:num_row

for j = 1:num_col

[x,y] = pol2cart(theta+j*k+i*k , r);

x = x+i;

y = y+j;

patch(x,y,[0.7 0.2 0.9],'edgecolor','flat'...

,'linewidth',1.5,'FaceVertexCData',colmap);

end

end

set(gcf,'color',[0.4 0.6 0.7]);

axis off equal

%% Optical Illusion

% Script to make simple optical illusion using sqaures and

% cirlces.

%Draw the circles

num_points = 250;

t = 0 : 2*pi/num_points : 2*pi;

r = 10; %radius

[x,y] = pol2cart(t,r);

for k=1:0.2:10

[x,y]=pol2cart(t,k);

patch(x,y,'r','facecolor','none','edgecolor',[0 0 0])

end

%Draw the squares

x2 = [-1 1 1 -1];

y2 = [-1 -1 1 1];

for k = 1:7

patch(k*x2,k*y2,'r','facecolor','none','edgecolor',[1 0 0])

end

axis equal off

%% Optical Illusion

% Script to make simple optical illusion using straight lines

t = linspace(0,2*pi,150);

r = 10;

[x,y] = pol2cart(t,r);

%Draw radial lines

plot([zeros(1,length(x));x],[zeros(1,length(y));y],'color',[0 0 0]),hold on

% Draw lines running parallel to x and y axis

x2=[-2.5 2.5];

y2=[-11 -11];

line([x2;x2],[-y2;y2],'color',[1 0 0])

line([y2;-y2],[x2;x2],'color',[1 0 0])

plot(0,0,'.','markersize',150,'color',[1 1 1])

axis([-11 11 -11 11])

axis equal off