TRACKPixx Demo 2 – Recording and plotting pursuit data with the TRACKPixx3¶
Note
This demo requires TRACKPixx Revision 18 or later. You can check for recent firmware updates at vpixx.com/whatsnew
This simple eye-tracking demo displays a dot moving in a circle around the center of the screen. We record 5 seconds of pursuit data. This data is then superimposed over the target path and saved into a .csv file for further analysis in your software of choice.
At the beginning of the demo there is an optional calibration step. This step calls TPxTrackpixx3CalibrationTesting
, which implements a standard MATLAB TRACKPixx3 calibration script. The tracker must be calibrated for every new participant. We also recommend calibrating after a participant moves away from the chinrest.
Following calibration the demo wakes the TRACKPixx3, sets up a tracking schedule with SetupTPxSchedule
, and starts this schedule with StartTpxSchedule
when the target appears. This schedule controls recording of eye data, which is stored on a data buffer on the DATAPixx3 controller. We record 5 seconds of pursuit data, and plot this in MATLAB for inspection. Eye data is also written into a .csv file for further analysis.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 | function TPxPursuitTracking(initRequired)
%
% This demo draws a moving dot for 5 seconds, and tracks the smooth
% pursuit movement of the viewer. Data is plotted and saved.
% Most recently tested with:
% -- TRACKPixx3 firmware revision 18
% -- DATAPixx3 firmware revision 19
% -- MATLAB version 9.6.0.1150989 (R2019a)
% -- Psychtoolbox verison 3.0.15
% -- Datapixx Toolbox version 3.7.5735
% -- Windows 10 version 1903, 64bit
% Oct 22, 2019 lef Written
% Mar 26 2020 lef Updated
%% Step 1 - Initialize (if needed)
if nargin==0
initRequired=1;
end
% Get some user input
fileName= input('Enter participant name: ', 's');
fileID = [fileName '.mat'];
%If a calibration is needed, call the calibration script
if initRequired
fprintf('\nInitialization required\n\nCalibrating the device...');
TPxTrackpixx3CalibrationTesting;
end
%Connect to TRACKPixx3
Datapixx('Open');
Datapixx('SetTPxAwake');
Datapixx('RegWrRd');
%% Step 2 - Set up the TRACKPixx recording schedule
Datapixx('SetupTPxSchedule');
%write all commands to the DATAPixx device register
Datapixx('RegWrRd');
%% Step 3 - Show our image and record eye position
AssertOpenGL;
%set our recording time
viewingTime = 5;
%open window
Screen('Preference', 'SkipSyncTests', 1 );
screenID = 2; %change to switch display
[windowPtr, rect]=Screen('OpenWindow', screenID, [0,0,0]);
Screen('BlendFunction', windowPtr, 'GL_SRC_ALPHA', 'GL_ONE_MINUS_SRC_ALPHA');
Screen('Flip',windowPtr);
%determine a trajectory
radius = 300; %in pixels for now
targetSize = 20;
trajectory = 0 : 0.01 : 2*pi;
%show instructions to participant
text_to_draw = ['PURSUIT DEMO:\n\nFollow the target with your eyes.\n\nPress any key to start.'];
DrawFormattedText(windowPtr, text_to_draw, 'center', 700, 255);
Screen('Flip', windowPtr);
%wait for participant to continue
[~, ~, ~] = KbPressWait;
Screen('Flip', windowPtr);
WaitSecs(1);
% %set up recording to start on the same frame flip that shows the image.
% %We also get the time of the flip using a Marker which saves a time of the
% %frame flip on the DATAPixx clock
Datapixx('StartTPxSchedule');
Datapixx('SetMarker');
Datapixx('RegWrVideoSync');
startTime = NaN;
currentTime = NaN;
positionCounter = 0;
while ~((currentTime - startTime) >= viewingTime)
positionCounter = positionCounter + 1;
%if we get to the end of our trajectory, restart
if positionCounter > numel(trajectory)
positionCounter = 1;
end
%draw our image and flip
centerX = rect(3)/2 + radius*(cos(trajectory(positionCounter)));
centerY = rect(4)/2 + radius*(sin(trajectory(positionCounter)));
Screen('FillOval', windowPtr, [255,50,50], [centerX-targetSize/2, centerY-targetSize/2, centerX+targetSize/2, centerY+targetSize/2 ]);
Screen('Flip', windowPtr);
Datapixx('RegWrRd');
startTime = Datapixx('GetMarker');
currentTime = Datapixx('GetTime');
end
%stop recording
Datapixx('StopTPxSchedule');
Datapixx('RegWrRd');
endTime = Datapixx('GetTime');
%read in eye data
status = Datapixx('GetTPxStatus');
toRead = status.newBufferFrames;
[bufferData, ~, ~] = Datapixx('ReadTPxData', toRead);
%bufferData is formatted as follows:
%1 --- Timetag (in seconds)
%2 --- Left Eye X (in pixels)
%3 --- Left Eye Y (in pixels)
%4 --- Left Pupil Diameter (in pixels)
%5 --- Right Eye X (in pixels)
%6 --- Right Eye Y (in pixels)
%7 --- Right Pupil Diameter (in pixels)
%8 --- Digital Input Values (24 bits)
%9 --- Left Blink Detection (0=no, 1=yes)
%10 --- Right Blink Detection (0=no, 1=yes)
%11 --- Digital Output Values (24 bits)
%12 --- Left Eye Fixation Flag (0=no, 1=yes)
%13 --- Right Eye Fixation Flag (0=no, 1=yes)
%14 --- Left Eye Saccade Flag (0=no, 1=yes)
%15 --- Right Eye Saccade Flag (0=no, 1=yes)
%16 --- Message code (integer)
%17 --- Left Eye Raw X (in pixels)
%18 --- Left Eye Raw Y (in pixels)
%19 --- Right Eye Raw X (in pixels)
%20 --- Right Eye Raw Y (in pixels)
%IMPORTANT: "RIGHT" and "LEFT" refer to the right and left eyes shown
%in the console overlay. In tabletop and MEG setups, this view is
%inverted. This means "RIGHT" in our labelling convention corresponds
%to the participant's left eye. Similarly "LEFT" in our convention
%refers to left on the screen, which corresponds to the participant's
%right eye.
%If you are using an MRI setup with an inverting mirror, "RIGHT" will
%correspond to the participant's right eye.
%save eye data from trial as a table in the trial structure
eyeData = array2table(bufferData, 'VariableNames', {'TimeTag', 'LeftEyeX', 'LeftEyeY', 'LeftPupilDiameter', 'RightEyeX', 'RightEyeY', 'RightPupilDiameter',...
'DigitalIn', 'LeftBlink', 'RightBlink', 'DigitalOut', 'LeftEyeFixationFlag', 'RightEyeFixationFlag', 'LeftEyeSaccadeFlag', 'RightEyeSaccadeFlag',...
'MessageCode', 'LeftEyeRawX', 'LeftEyeRawY', 'RightEyeRawX', 'RightEyeRawY'});
%get some other trial data
pursuitTime = endTime - startTime;
%interim save
save(fileID, 'eyeData', 'pursuitTime');
%Close everything
Screen('Closeall');
Datapixx('SetTPxSleep');
Datapixx('RegWrRd');
Datapixx('Close');
%% Step 4 - Plot some gaze paths
fprintf('\nRecording lasted %f seconds', pursuitTime);
figure();
plot(radius*(cos(trajectory)), radius*(sin(trajectory)), 'Color', [0.5, 0.5, 0.5], 'LineWidth', targetSize/2);
hold on
x = eyeData.LeftEyeX(:,:);
y = eyeData.LeftEyeY(:,:);
plot(x,y, 'ob', 'linewidth', 1, 'markersize', 1);
x = eyeData.RightEyeX(:,:);
y = eyeData.RightEyeY(:,:);
plot(x,y, 'or', 'linewidth', 1, 'markersize', 1);
xlim([-rect(3)/2, rect(3)/2]);
ylim([-rect(4)/2, rect(4)/2]);
legend({'Target path','Left eye', 'Right Eye'});
xlabel('X position (pixels)');
ylabel('Y position (pixels)');
title('Gaze path for 5s smooth pursuit');
%% Step 5 - Write data to csv for subsequent analysis
savefig(fileName);
csvFileID = [fileName '_Results.csv'];
writetable(eyeData, csvFileID);
end
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