Displaying Gabor patches at 480 Hz

In this demo, we design a stimuli to run at 480 Hz on the PROPixx. To display at 480 Hz, we limit our resolution to 1/4 of the screen to display 4 times faster. Indeed, your stimulus needs to be created as follows:

Quadrant 1	Quadrant 2
Quadrant 3	Quadrant 4

We simply generate a window of size (960, 540) and we move it to the right quadrant. In one frame, we animate the stimulus 4 times, once for each quadrant. We send a 120 Hz signal that has 4 frames of information, allowing us to display at 480 Hz.

For 1440 Hz display, the technique is the same, but we use the colour information of each quadrant to create the equivalent of twelve frames in one. Frame 1 would be Quadrant 1 Red, frame 2 is Quadrant 2 Red, and on until green and then finally quadrant 1 to 4 blue.

To set the PROPixx in a different mode, we use a sequencer, Datapixx('SetPropixxDlpSequenceProgram', 2);, the 2 is for 480 Hz, 5 for 1440 Hz, 0 for normal display.

In this demo we create a Gabors that we scale for every Gabors we want, then we move them randomly in the resolution. We animate the Gabors 4 times per frame to create the 480 Hz animation. We animate everything as in Quadrant 1 and move them to the respective quadrant.

At the end of the script, we must put back the normal sequencer, Datapixx('SetPropixxDlpSequenceProgram', 0);.

MATLAB

function DatapixxShowGabor(frames, nbr_of_Gabor, win)
% function DatapixxShowGabor(frames = 4800, nbr_of_Gabor = 200, win)
%
% This has been inspired by GaboriumDemo.m from Psychtoolbox.
%
% This demo constructs a gabor aquarium at 480 Hz. It displays the Gabor
% for a set amount of frames given by the frames argument. The number of gabor
% is determined by nbr_of_Gabor and the max amount depends on the speed
% of your computer. 
%
% frames --         Number of frames to animate the stimuli for (optional, 
%                   default is 4800)
% nbr_of_Gabor --   Number of Gabor to be in the stimuli (optional, default
%                   is 200)
% win --            Handle to the win (optional, default is full screen)
%
% Oct 29, 2014      dml     Written
% Mar 23, 2018      dml     Updated

% Initialize the PROPixx to 480 Hz

Datapixx('Open');
Datapixx('SetPropixxDlpSequenceProgram', 2); % 2 for 480, 5 for 1440 Hz, 0 for normal
Datapixx('RegWrRd');


if nargin < 3 || isempty(win)
    PsychImaging('PrepareConfiguration');
    PsychImaging('AddTask', 'General', 'FloatingPoint32BitIfPossible');
    screenid = max(Screen('Screens'));
    [win win_rect] = PsychImaging('OpenWindow', screenid, 128);
end

if nargin < 2 || isempty(nbr_of_Gabor)
    nbr_of_Gabor = 100;
end

if nargin < 1 || isempty(frames)
    frames = 4800;
end


% Set the transparency for gabor patch
Screen('BlendFunction', win, GL_SRC_ALPHA, GL_ONE);
% Get refresh rate
ifi = Screen('GetFlipInterval', win);

%Generate a Gabor patch (from GaboriumDemo.m)
s = 32;
res = 2*[s s];
phase = 0;
sc = 5;
freq = 0.05;
tilt = 0;
contrast = 5;
x=res(1)/2;
y=res(2)/2;
sf = freq;
[gab_x gab_y] = meshgrid(0:(res(1)-1), 0:(res(2)-1));
a=cos(deg2rad(tilt))*sf*360;
b=sin(deg2rad(tilt))*sf*360;
multConst=1/(sqrt(2*pi)*sc);
x_factor=-1*(gab_x-x).^2;
y_factor=-1*(gab_y-y).^2;
sinWave=sin(deg2rad(a*(gab_x - x) + b*(gab_y - y)+phase));
varScale=2*sc^2;
m=contrast*(multConst*exp(x_factor/varScale+y_factor/varScale).*sinWave)';

%Transform the gabors into texture
gabortex=Screen('MakeTexture', win, m, [], [], 2);
texrect = Screen('Rect', gabortex);
inrect = repmat(texrect', 1, nbr_of_Gabor);

% Create the array for the 4 quadrants gabor
dstRects = zeros(4, nbr_of_Gabor);
dstRects_q2 = zeros(4, nbr_of_Gabor);
dstRects_q3 = zeros(4, nbr_of_Gabor);
dstRects_q4 = zeros(4, nbr_of_Gabor);
srcRects = [];
rotAngles = rand(1, nbr_of_Gabor) * 360;

% Create the right amount of gabors, and scale them randomly
for i=1:nbr_of_Gabor
    scale(i) = 2*(0.1 + 0.9 * randn);
    dstRects(:, i) = CenterRectOnPoint(texrect * scale(i), rand * 1920/2, rand * 1080/2)';
end

% Initial flip
vbl = Screen('Flip', win);
number_of_frames = 1;

% Stimulus
while number_of_frames < frames

    % FRAME 1
    if number_of_frames > frames
        vbl = Screen('Flip', win, vbl + 0.5 * ifi);
        break;
    end
    Screen('DrawTextures', win, gabortex, srcRects, dstRects, rotAngles, [], 0.5, [], [], 0);
    number_of_frames = number_of_frames + 1;
    
    % Animate
    rotAngles = rotAngles + 1 * randn(1, nbr_of_Gabor);
    [x y] = RectCenterd(dstRects);
    x = mod(x + cos(rotAngles/360*2*pi), 1920/2);
    y = mod(y + sin(rotAngles/360*2*pi), 1080/2);
    dstRects_q2 = CenterRectOnPointd(inrect .*  repmat(scale,4,1), x, y);

    % Move to Q2
    dstRects_q2(1,:) = dstRects_q2(1,:) + 1920/2;
    dstRects_q2(3,:) = dstRects_q2(3,:) + 1920/2;

    % FRAME 2
    if number_of_frames > frames
        vbl = Screen('Flip', win, vbl + 0.5 * ifi);
        break;
    end
    Screen('DrawTextures', win, gabortex, srcRects, dstRects_q2, rotAngles, [], 0.5, [], [], 0);
    number_of_frames = number_of_frames + 1;
    
    % animate
    rotAngles = rotAngles + 1 * randn(1, nbr_of_Gabor);
    [x y] = RectCenterd(dstRects_q2);
    x = mod(x + cos(rotAngles/360*2*pi), 1920/2);
    y = mod(y + sin(rotAngles/360*2*pi), 1080/2);
    dstRects_q3 = CenterRectOnPointd(inrect .* repmat(scale,4,1), x, y);

    % Move to Q3
    dstRects_q3(2,:) = dstRects_q3(2,:) + 1080/2;
    dstRects_q3(4,:) = dstRects_q3(4,:) + 1080/2;

    % FRAME 3
    if number_of_frames > frames
        vbl = Screen('Flip', win, vbl + 0.5 * ifi);
        break;
    end
    Screen('DrawTextures', win, gabortex, srcRects, dstRects_q3, rotAngles, [], 0.5, [], [], 0);
    number_of_frames = number_of_frames + 1;

    % Animate
    rotAngles = rotAngles + 1 * randn(1, nbr_of_Gabor);
    [x y] = RectCenterd(dstRects_q3);
    x = mod(x + cos(rotAngles/360*2*pi), 1920/2);
    y = mod(y + sin(rotAngles/360*2*pi), 1080/2);
    dstRects_q4 = CenterRectOnPointd(inrect .* repmat(scale,4,1), x, y);

    % Move to Q4
    dstRects_q4(1,:) = dstRects_q4(1,:) + 1920/2;
    dstRects_q4(2,:) = dstRects_q4(2,:) + 1080/2;
    dstRects_q4(3,:) = dstRects_q4(3,:) + 1920/2;
    dstRects_q4(4,:) = dstRects_q4(4,:) + 1080/2;

    % FRAME 4
    if number_of_frames > frames
        vbl = Screen('Flip', win, vbl + 0.5 * ifi);
        break;
    end
    Screen('DrawTextures', win, gabortex, srcRects, dstRects_q4, rotAngles, [], 0.5, [], [], 0);
    number_of_frames = number_of_frames + 1;

    % animate for next frame
    rotAngles = rotAngles + 1 * randn(1, nbr_of_Gabor);
    [x y] = RectCenterd(dstRects_q4);
    x = mod(x + cos(rotAngles/360*2*pi), 1920/2);
    y = mod(y + sin(rotAngles/360*2*pi), 1080/2);
    dstRects = CenterRectOnPointd(inrect .* repmat(scale,4,1), x, y);

    % Update the four Qudrants
    vbl = Screen('Flip', win, vbl + 0.5 * ifi);

    [pressed dummy keycode] = KbCheck;
    if pressed
        break;
    end
    
end

% Blank screen
Screen('Flip', win);

% Exit on escape
KbName('UnifyKeyNames');
escapeKey = KbName('ESCAPE');
while 1
 % Check the state of the keyboard.
    [ keyIsDown, ~, keyCode ] = KbCheck;
 if keyIsDown
    if keyCode(escapeKey)
        Screen('CloseAll')
        break;
    end
 end
end

%Restore PROPixx State
Datapixx('SetPropixxDlpSequenceProgram', 0);
Datapixx('RegWrRd');
Datapixx('close');
clear all;