How can I change this gabor patch so that the color of the outer circles fade away

% Animates sinusoidal concentric grating

clear all;

n=100;

M=moviein(n); % for Matlab movie animation

f=1000; % frequency

w=2*pi*f;

t=linspace(pi/15/w,2*pi/w,100); %30 time steps per period

c=800;

k=w/c;

a=0.1; % sphere radius

x=linspace(-2,2,100); % 4 m x 4 m area, with 100 points

y=linspace(-2,2,100);

for m=1:100

for l=1:100

r(m,l)=sqrt((x(m)^2)+(y(l)^2));

if r(m,l)>=a

pt(m,l)=exp(1i*k*(r(m,l)-a))/r(m,l);

else

pt(m,l)=1/a; % for visualization purposes

%if r(m,l)>=1

end

end

end

pmag=sqrt((abs(pt))); % 1/4 power of amplitude for better contrast

pphase=angle(pt);

clim=max(max(pmag));

V=[-clim clim]; % sets color scheme

pt=pmag.*exp(1i*pphase); % red: maximum positive

% blue: minimum negative pressure

figure(1)

axis equal % to eliminate distortion

axis([-2 2 -2 2])

for l=1:100

pt2=real(pt*exp(-1i*w*t(l)));

h=pcolor(x,y,pt2);

colormap(gray(100))

axis equal

xlabel('x');

ylabel('y');

shading interp;

%caxis(V);

axis([-2 2 -2 2])

M(:,l)=getframe;

%

% filnme=strcat('spher',int2str(l));

% eval(['print -dbitmap ' filnme ' -f']);

end

Hello,

I am currently working on my bachelor thesis and I need to modify this code in order to get the color of the outer circles fade away.

Maybe someone got an idea on how to tackle this problem.

Thanks in advance!

Answer 1

[Abhinaya Kennedy]

Hello Denis,

I understand that you need to modify your code to get the colour of the outer circles to fade away.

The 'Alpha' property allows you to add transparency to objects in axes. Here is the modified code.

clear all;
n = 100;
M = moviein(n); % for Matlab movie animation
f = 1000; % frequency
w = 2 * pi * f;
t = linspace(pi / 15 / w, 2 * pi / w, 100); % 30 time steps per period
c = 800;
k = w / c;
a = 0.1; % sphere radius
x = linspace(-2, 2, 100); % 4 m x 4 m area, with 100 points
y = linspace(-2, 2, 100);

for m = 1:100
    for l = 1:100
        r(m, l) = sqrt((x(m)^2) + (y(l)^2));
        if r(m, l) >= a
            pt(m, l) = exp(1i * k * (r(m, l) - a)) / r(m, l);
        else
            pt(m, l) = 1 / a; % for visualization purposes
        end
    end
end

pmag = sqrt((abs(pt))); % 1/4 power of amplitude for better contrast
pphase = angle(pt);
clim = max(max(pmag));
V = [-clim clim]; % sets color scheme
pt = pmag .* exp(1i * pphase); % red: maximum positive
% blue: minimum negative pressure

figure(1)
axis equal % to eliminate distortion
axis([-2 2 -2 2])

for l = 1:100
    pt2 = real(pt * exp(-1i * w * t(l)));
    % Fade the color of outer circles
    colorFade = 1 - r / max(max(r));
    h = pcolor(x, y, pt2);
    colormap(gray(100))
    axis equal
    xlabel('x');
    ylabel('y');
    shading interp;
    %caxis(V);
    axis([-2 2 -2 2])
    % Apply color fade to the plot
    set(h, 'FaceAlpha', 'interp', 'AlphaData', colorFade);
    M(:, l) = getframe;
end

In this modified code, the 'colorFade' variable is introduced to control the fading of color based on the distance from the center. The color fade is calculated as 1 - r / max(max(r)), where 'r' represents the distance from the center of the circles. The 'AlphaData' property of the plot is then set to 'colorFade' to apply the fading effect.

Adjust the code according to your specific requirements and preferences to achieve the desired fading effect on the outer circles of the Gabor patch.

Here is a link to find out more about the 'Alpha' property: https://www.mathworks.com/help/releases/R2023a/matlab/ref/alpha.html?s_tid=doc_srchtitle

Hope this answers your queries.