% Clear the workspace and the screen
sca;
close all;
clear;

% Here we call some default settings for setting up Psychtoolbox
PsychDefaultSetup(2);

% Get the screen numbers
screens = Screen('Screens');

% Draw to the external screen if avaliable
screenNumber = max(screens);

% Define black and white
white = WhiteIndex(screenNumber);
black = BlackIndex(screenNumber);
grey = GrayIndex(screenNumber);
darkGrey = white * 0.25;

% Open an on screen window
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, darkGrey);

% Get the size of the on screen window
[screenXpixels, screenYpixels] = Screen('WindowSize', window);

% Query the frame duration
ifi = Screen('GetFlipInterval', window);

% Set up alpha-blending for smooth (anti-aliased) lines
Screen('BlendFunction', window, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');

% Get the centre coordinate of the window
[xCenter, yCenter] = RectCenter(windowRect);

% Line width of the lines around the squares: this is like the "motar" of
% the brick wall
morterWidth = 3;

% Dimensions: the grid will be this plus one in width and height
dim = 5;

% A basic way to make sure this scales to the screen
gridSqSize = screenYpixels * 0.3 / (dim - 1);

% Screen positions for the centre of all of our sqaures
[xposOrig, yposOrig] = meshgrid(-dim:dim, -dim:dim);
xpos = xposOrig .* gridSqSize + xCenter;
ypos = yposOrig .* gridSqSize + yCenter;

% Define the black and white pattern of the grid
grid = repmat(reshape(mod(xposOrig + yposOrig, 2), 1, numel(xposOrig)), 3, 1);

% Dimensions and count
[s1, s2] = size(ypos);
numSquares = numel(ypos);

% Our wall will oscilate with a sine wave function to the left and right
% of the screen. These are the parameters for the sine wave
% See: http://en.wikipedia.org/wiki/Sine_wave
amplitude = gridSqSize;
frequency = 0.1;
angFreq = 2 * pi * frequency;
startPhase = 0;
time = 0;

% We will update the animation on each frame
waitframes = 1;

% Flip to sync to screen refresh
vbl = Screen('Flip', window);

% Loop the animation until a key is pressed
while ~KbCheck(-1)

    % Rectangle positions for our squares. The larger squares are needed for
    % the motar to be the same width at the edges of the grid.
    % Another option, instead of only drawing background squares at the edges, is
    % simply to draw them all. The drawing will not be very much overhead.
    allRectsSquares = nan(numSquares, 4);
    allRectsMortar = nan(numSquares, 4);
    ticker = 0;
    for i = 1:s1

        % We shift every other line laterally to make the Cafe Wall illusion
        if mod(i, 2) == 1
            adder = gridSqSize * sin(angFreq * time + startPhase);
        else
            adder = 0;
        end

        for ii = 1:s2

            % Increment ticker
            ticker = ticker + 1;

            % Make this square coordinates
            allRectsSquares(ticker, :) = CenterRectOnPointd([0 0 gridSqSize gridSqSize],...
                xpos(i, ii) + adder, ypos(i, ii));

            % We only want additional background squares for the outer edges
            if i == 1 || ii == 1 || i == s1 || ii == s2
                allRectsMortar(ticker, :) = CenterRectOnPointd([0 0 gridSqSize + morterWidth gridSqSize + morterWidth],...
                    xpos(i, ii) + adder, ypos(i, ii));
            end

        end

    end

    % Remove the nans
    allRectsMortar = allRectsMortar(all(~isnan(allRectsMortar), 2), :);

    % Draw the background squres to make the edge motar work
    Screen('FillRect', window, grey, allRectsMortar');

    % Draw the black and white squares
    Screen('FillRect', window, grid, allRectsSquares');

    % Draw the mortar
    Screen('FrameRect', window, grey, allRectsSquares', morterWidth);

    % Flip to the screen
    vbl  = Screen('Flip', window, vbl + (waitframes - 0.5) * ifi);

    % Increment time
    time = time + ifi;

end

% Clear the screen
sca;

Published with MATLAB® R2024b