tracker.start_recording()
# show the image
pygame.display.flip()
tracker.log_message("image_on")
tracker.log_message(imgname)
# wait for a bit
pygame.time.wait(5000)
# show a blank screen
disp.fill(BGC)
pygame.display.flip()
tracker.log_message("image_off")
# stop recording
tracker.stop_recording()
# wait for a bit
pygame.time.wait(2000)
# # # # #
# CLOSE
# close connection to the tracker
tracker.close()
# close the display
pygame.quit()
class EyeTribeTracker(BaseEyeTracker):
"""A class for EyeTribeTracker objects"""
def __init__(self, display, logfile=LOGFILE, eventdetection=EVENTDETECTION, \
saccade_velocity_threshold=35, saccade_acceleration_threshold=9500, \
**args):
"""Initializes the EyeTribeTracker object
arguments
display -- a pygaze.display.Display instance
keyword arguments
logfile -- logfile name (string value); note that this is the
name for the eye data log file (default = LOGFILE)
"""
# try to copy docstrings (but ignore it if it fails, as we do
# not need it for actual functioning of the code)
try:
copy_docstr(BaseEyeTracker, EyeTribeTracker)
except:
# we're not even going to show a warning, since the copied
# docstring is useful for code editors; these load the docs
# in a non-verbose manner, so warning messages would be lost
pass
# object properties
self.disp = display
self.screen = Screen()
self.dispsize = DISPSIZE # display size in pixels
self.screensize = SCREENSIZE # display size in cm
self.kb = Keyboard(keylist=['space', 'escape', 'q'], timeout=1)
self.errorbeep = Sound(osc='saw',freq=100, length=100)
# output file properties
self.outputfile = logfile
# eye tracker properties
self.connected = False
self.recording = False
self.errdist = 2 # degrees; maximal error for drift correction
self.pxerrdist = 30 # initial error in pixels
self.maxtries = 100 # number of samples obtained before giving up (for obtaining accuracy and tracker distance information, as well as starting or stopping recording)
self.prevsample = (-1,-1)
self.prevps = -1
# event detection properties
self.fixtresh = 1.5 # degrees; maximal distance from fixation start (if gaze wanders beyond this, fixation has stopped)
self.fixtimetresh = 100 # milliseconds; amount of time gaze has to linger within self.fixtresh to be marked as a fixation
self.spdtresh = saccade_velocity_threshold # degrees per second; saccade velocity threshold
self.accthresh = saccade_acceleration_threshold # degrees per second**2; saccade acceleration threshold
self.eventdetection = eventdetection
self.set_detection_type(self.eventdetection)
self.weightdist = 10 # weighted distance, used for determining whether a movement is due to measurement error (1 is ok, higher is more conservative and will result in only larger saccades to be detected)
# connect to the tracker
self.eyetribe = EyeTribe(logfilename=logfile)
# get info on the sample rate
self.samplerate = self.eyetribe._samplefreq
self.sampletime = 1000.0 * self.eyetribe._intsampletime
# initiation report
self.log("pygaze initiation report start")
self.log("display resolution: %sx%s" % (self.dispsize[0],self.dispsize[1]))
self.log("display size in cm: %sx%s" % (self.screensize[0],self.screensize[1]))
self.log("samplerate: %.2f Hz" % self.samplerate)
self.log("sampletime: %.2f ms" % self.sampletime)
self.log("fixation threshold: %s degrees" % self.fixtresh)
self.log("speed threshold: %s degrees/second" % self.spdtresh)
self.log("acceleration threshold: %s degrees/second**2" % self.accthresh)
self.log("pygaze initiation report end")
def calibrate(self):
"""Calibrates the eye tracking system
arguments
None
keyword arguments
None
returns
success -- returns True if calibration succeeded, or False if
not; in addition a calibration log is added to the
log file and some properties are updated (i.e. the
thresholds for detection algorithms)
"""
# CALIBRATION
# determine the calibration points
calibpoints = []
for x in [0.1,0.5,0.9]:
for y in [0.1,0.5,0.9]:
calibpoints.append((int(x*self.dispsize[0]),int(y*self.dispsize[1])))
random.shuffle(calibpoints)
# show a message
self.screen.clear()
self.screen.draw_text(text="Press Space to start the calibration or Q to quit.")
self.disp.fill(self.screen)
self.disp.show()
# wait for keyboard input
key, keytime = self.kb.get_key(keylist=['q','space'], timeout=None, flush=True)
if key == 'q':
quited = True
else:
quited = False
# run until the user is statisfied, or quits
calibrated = False
calibresult = None
while not quited and not calibrated:
# start a new calibration
self.eyetribe.calibration.start(pointcount=len(calibpoints))
# loop through calibration points
for cpos in calibpoints:
self.draw_calibration_target(cpos[0], cpos[1])
# wait for a bit to allow participant to start looking at
# the calibration point (#TODO: space press?)
clock.pause(1000)
# start calibration of point
self.eyetribe.calibration.pointstart(cpos[0],cpos[1])
# wait for a second
clock.pause(1000)
# stop calibration of this point
result = self.eyetribe.calibration.pointend()
# the final calibration point returns a dict (does it?)
if type(result) == dict:
calibresult = copy.deepcopy(result)
# check if the Q key has been pressed
if self.kb.get_key(keylist=['q'],timeout=10,flush=False)[0] == 'q':
# abort calibration
self.eyetribe.calibration.abort()
# set quited variable and break this for loop
quited = True
break
# retry option if the calibration was aborted
if quited:
# show retry message
self.screen.clear()
self.screen.draw_text("Calibration aborted. Press Space to restart, or 'Q' to quit.")
self.disp.fill(self.screen)
self.disp.show()
# get input
key, keytime = self.kb.get_key(keylist=['q','space'], timeout=None, flush=True)
if key == 'space':
# unset quited Boolean
quited = False
# skip further processing
continue
# get the calibration result if it was not obtained yet
if type(calibresult) != dict:
# empty display
self.disp.fill()
self.disp.show()
# allow for a bit of calculation time
clock.pause(2000)
# get the result
calibresult = self.eyetribe._tracker.get_calibresult()
# results
# clear the screen
self.screen.clear()
# draw results for each point
if type(calibresult) == dict:
for p in calibresult['calibpoints']:
# only draw the point if data was obtained
if p['state'] > 0:
# draw the mean error
self.screen.draw_circle(colour=(252,233,79), pos=(p['cpx'],p['cpy']), r=p['mepix'], pw=0, fill=True)
# draw the point
self.screen.draw_fixation(fixtype='dot', colour=(115,210,22), pos=(p['cpx'],p['cpy']))
# draw the estimated point
self.screen.draw_fixation(fixtype='dot', colour=(32,74,135), pos=(p['mecpx'],p['mecpy']))
# annotate accuracy
self.screen.draw_text(text=str(p['acd']), pos=(p['cpx']+10,p['cpy']+10), fontsize=12)
# if no data was obtained, draw the point in red
else:
self.screen.draw_fixation(fixtype='dot', colour=(204,0,0), pos=(p['cpx'],p['cpy']))
# draw box for averages
self.screen.draw_rect(colour=(238,238,236), x=int(self.dispsize[0]*0.15), y=int(self.dispsize[1]*0.2), w=400, h=200, pw=0, fill=True)
# draw result
if calibresult['result']:
self.screen.draw_text(text="calibration is successful", colour=(115,210,22), pos=(int(self.dispsize[0]*0.25),int(self.dispsize[1]*0.25)), fontsize=12)
else:
self.screen.draw_text(text="calibration failed", colour=(204,0,0), pos=(int(self.dispsize[0]*0.25),int(self.dispsize[1]*0.25)), fontsize=12)
# draw average accuracy
self.screen.draw_text(text="average error = %.2f degrees" % (calibresult['deg']), colour=(211,215,207), pos=(int(self.dispsize[0]*0.25),int(self.dispsize[1]*0.25+20)), fontsize=12)
# draw input options
self.screen.draw_text(text="Press Space to continue, or 'R' to restart.", colour=(211,215,207), pos=(int(self.dispsize[0]*0.25),int(self.dispsize[1]*0.25+40)), fontsize=12)
else:
self.screen.draw_text(text="Calibration failed, press 'R' to try again.")
# show the results
self.disp.fill(self.screen)
self.disp.show()
# wait for input
key, keytime = self.kb.get_key(keylist=['space','r'], timeout=None, flush=True)
# process input
if key == 'space':
calibrated = True
# calibration failed if the user quited
if quited:
return False
# NOISE CALIBRATION
# get all error estimates (pixels)
var = []
for p in calibresult['calibpoints']:
# only draw the point if data was obtained
if p['state'] > 0:
var.append(p['mepix'])
noise = sum(var) / float(len(var))
self.pxdsttresh = (noise, noise)
# AFTERMATH
# store some variables
pixpercm = (self.dispsize[0]/float(self.screensize[0]) + self.dispsize[1]/float(self.screensize[1])) / 2
screendist = SCREENDIST
# calculate thresholds based on tracker settings
self.accuracy = ((calibresult['Ldeg'],calibresult['Ldeg']), (calibresult['Rdeg'],calibresult['Rdeg']))
self.pxerrdist = deg2pix(screendist, self.errdist, pixpercm)
self.pxfixtresh = deg2pix(screendist, self.fixtresh, pixpercm)
self.pxaccuracy = ((deg2pix(screendist, self.accuracy[0][0], pixpercm),deg2pix(screendist, self.accuracy[0][1], pixpercm)), (deg2pix(screendist, self.accuracy[1][0], pixpercm),deg2pix(screendist, self.accuracy[1][1], pixpercm)))
self.pxspdtresh = deg2pix(screendist, self.spdtresh/1000.0, pixpercm) # in pixels per millisecond
self.pxacctresh = deg2pix(screendist, self.accthresh/1000.0, pixpercm) # in pixels per millisecond**2
# calibration report
self.log("pygaze calibration report start")
self.log("accuracy (degrees): LX=%s, LY=%s, RX=%s, RY=%s" % (self.accuracy[0][0],self.accuracy[0][1],self.accuracy[1][0],self.accuracy[1][1]))
self.log("accuracy (in pixels): LX=%s, LY=%s, RX=%s, RY=%s" % (self.pxaccuracy[0][0],self.pxaccuracy[0][1],self.pxaccuracy[1][0],self.pxaccuracy[1][1]))
self.log("precision (RMS noise in pixels): X=%s, Y=%s" % (self.pxdsttresh[0],self.pxdsttresh[1]))
self.log("distance between participant and display: %s cm" % screendist)
self.log("fixation threshold: %s pixels" % self.pxfixtresh)
self.log("speed threshold: %s pixels/ms" % self.pxspdtresh)
self.log("acceleration threshold: %s pixels/ms**2" % self.pxacctresh)
self.log("pygaze calibration report end")
return True
def close(self):
"""Neatly close connection to tracker
arguments
None
returns
Nothing -- saves data and sets self.connected to False
"""
# close connection
self.eyetribe.close()
self.connected = False
def connected(self):
"""Checks if the tracker is connected
arguments
None
returns
connected -- True if connection is established, False if not;
sets self.connected to the same value
"""
res = self.eyetribe._tracker.get_trackerstate()
if res == 0:
self.connected = True
else:
self.connected = False
return self.connected
def drift_correction(self, pos=None, fix_triggered=False):
"""Performs a drift check
arguments
None
keyword arguments
pos -- (x, y) position of the fixation dot or None for
a central fixation (default = None)
fix_triggered -- Boolean indicating if drift check should be
performed based on gaze position (fix_triggered
= True) or on spacepress (fix_triggered =
False) (default = False)
returns
checked -- Boolaan indicating if drift check is ok (True)
or not (False); or calls self.calibrate if 'q'
or 'escape' is pressed
"""
if pos == None:
pos = self.dispsize[0] / 2, self.dispsize[1] / 2
if fix_triggered:
return self.fix_triggered_drift_correction(pos)
self.draw_drift_correction_target(pos[0], pos[1])
pressed = False
while not pressed:
pressed, presstime = self.kb.get_key()
if pressed:
if pressed == 'escape' or pressed == 'q':
print("libeyetribe.EyeTribeTracker.drift_correction: 'q' or 'escape' pressed")
return self.calibrate()
gazepos = self.sample()
if ((gazepos[0]-pos[0])**2 + (gazepos[1]-pos[1])**2)**0.5 < self.pxerrdist:
return True
else:
self.errorbeep.play()
return False
def draw_drift_correction_target(self, x, y):
"""
Draws the drift-correction target.
arguments
x -- The X coordinate
y -- The Y coordinate
"""
self.screen.clear()
self.screen.draw_fixation(fixtype='dot', colour=FGC, pos=(x,y), pw=0,
diameter=12)
self.disp.fill(self.screen)
self.disp.show()
def draw_calibration_target(self, x, y):
self.draw_drift_correction_target(x, y)
def fix_triggered_drift_correction(self, pos=None, min_samples=10, max_dev=60, reset_threshold=30):
"""Performs a fixation triggered drift correction by collecting
a number of samples and calculating the average distance from the
fixation position
arguments
None
keyword arguments
pos -- (x, y) position of the fixation dot or None for
a central fixation (default = None)
min_samples -- minimal amount of samples after which an
average deviation is calculated (default = 10)
max_dev -- maximal deviation from fixation in pixels
(default = 60)
reset_threshold -- if the horizontal or vertical distance in
pixels between two consecutive samples is
larger than this threshold, the sample
collection is reset (default = 30)
returns
checked -- Boolaan indicating if drift check is ok (True)
or not (False); or calls self.calibrate if 'q'
or 'escape' is pressed
"""
self.draw_drift_correction_target(pos[0], pos[1])
if pos == None:
pos = self.dispsize[0] / 2, self.dispsize[1] / 2
# loop until we have sufficient samples
lx = []
ly = []
while len(lx) < min_samples:
# pressing escape enters the calibration screen
if self.kb.get_key()[0] in ['escape','q']:
print("libeyetribe.EyeTribeTracker.fix_triggered_drift_correction: 'q' or 'escape' pressed")
return self.calibrate()
# collect a sample
x, y = self.sample()
if len(lx) == 0 or x != lx[-1] or y != ly[-1]:
# if present sample deviates too much from previous sample, reset counting
if len(lx) > 0 and (abs(x - lx[-1]) > reset_threshold or abs(y - ly[-1]) > reset_threshold):
lx = []
ly = []
# collect samples
else:
lx.append(x)
ly.append(y)
if len(lx) == min_samples:
avg_x = sum(lx) / len(lx)
avg_y = sum(ly) / len(ly)
d = ((avg_x - pos[0]) ** 2 + (avg_y - pos[1]) ** 2)**0.5
if d < max_dev:
return True
else:
lx = []
ly = []
def get_eyetracker_clock_async(self):
"""Not supported for EyeTribeTracker (yet)"""
print("function not supported yet")
def log(self, msg):
"""Writes a message to the log file
arguments
ms -- a string to include in the log file
returns
Nothing -- uses native log function of iViewX to include a line
in the log file
"""
self.eyetribe.log_message(msg)
def log_var(self, var, val):
"""Writes a variable to the log file
arguments
var -- variable name
val -- variable value
returns
Nothing -- uses native log function of iViewX to include a line
in the log file in a "var NAME VALUE" layout
"""
msg = "var %s %s" % (var, val)
self.log(msg)
def prepare_drift_correction(self, pos):
"""Not supported for EyeTribeTracker (yet)"""
print("function not supported yet")
def pupil_size(self):
"""Return pupil size
arguments
None
returns
pupil size -- returns pupil diameter for the eye that is currently
being tracked (as specified by self.eye_used) or -1
when no data is obtainable
"""
# get newest pupil size
ps = self.eyetribe.pupil_size()
# invalid data
if ps == None:
return -1
# check if the new pupil size is the same as the previous
if ps != self.prevps:
# update the pupil size
self.prevps = copy.copy(ps)
return self.prevps
def sample(self):
"""Returns newest available gaze position
arguments
None
returns
sample -- an (x,y) tuple or a (-1,-1) on an error
"""
# get newest sample
s = self.eyetribe.sample()
# invalid data
if s == (None,None):
return (-1,-1)
# check if the new sample is the same as the previous
if s != self.prevsample:
# update the current sample
self.prevsample = copy.copy(s)
return self.prevsample
def send_command(self, cmd):
"""Sends a command to the eye tracker
arguments
cmd -- the command to be sent to the EyeTribe, which should
be a list with the following information:
[category, request, values]
returns
Nothing
"""
self.eyetribe._connection.request(cmd)
def start_recording(self):
"""Starts recording eye position
arguments
None
returns
Nothing -- sets self.recording to True when recording is
successfully started
"""
self.eyetribe.start_recording()
self.recording = True
def status_msg(self, msg):
"""Not supported for EyeTribeTracker (yet)"""
print("function not supported yet")
def stop_recording(self):
"""Stop recording eye position
arguments
None
returns
Nothing -- sets self.recording to False when recording is
successfully started
"""
self.eyetribe.stop_recording()
self.recording = False
def set_detection_type(self, eventdetection):
"""Set the event detection type to either PyGaze algorithms, or
native algorithms as provided by the manufacturer (only if
available: detection type will default to PyGaze if no native
functions are available)
arguments
eventdetection -- a string indicating which detection type
should be employed: either 'pygaze' for
PyGaze event detection algorithms or
'native' for manufacturers algorithms (only
if available; will default to 'pygaze' if no
native event detection is available)
returns -- detection type for saccades, fixations and
blinks in a tuple, e.g.
('pygaze','native','native') when 'native'
was passed, but native detection was not
available for saccade detection
"""
if eventdetection in ['pygaze','native']:
self.eventdetection = eventdetection
return ('pygaze','pygaze','pygaze')
def wait_for_event(self, event):
"""Waits for event
arguments
event -- an integer event code, one of the following:
3 = STARTBLINK
4 = ENDBLINK
5 = STARTSACC
6 = ENDSACC
7 = STARTFIX
8 = ENDFIX
returns
outcome -- a self.wait_for_* method is called, depending on the
specified event; the return values of corresponding
method are returned
"""
if event == 5:
outcome = self.wait_for_saccade_start()
elif event == 6:
outcome = self.wait_for_saccade_end()
elif event == 7:
outcome = self.wait_for_fixation_start()
elif event == 8:
outcome = self.wait_for_fixation_end()
elif event == 3:
outcome = self.wait_for_blink_start()
elif event == 4:
outcome = self.wait_for_blink_end()
else:
raise Exception("Error in libsmi.SMItracker.wait_for_event: eventcode %s is not supported" % event)
return outcome
def wait_for_blink_end(self):
"""Waits for a blink end and returns the blink ending time
arguments
None
returns
timestamp -- blink ending time in milliseconds, as
measured from experiment begin time
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer blink detection; PyGaze algorithm \
will be used")
# # # # #
# PyGaze method
blinking = True
# loop while there is a blink
while blinking:
# get newest sample
gazepos = self.sample()
# check if it's valid
if self.is_valid_sample(gazepos):
# if it is a valid sample, blinking has stopped
blinking = False
# return timestamp of blink end
return clock.get_time()
def wait_for_blink_start(self):
"""Waits for a blink start and returns the blink starting time
arguments
None
returns
timestamp -- blink starting time in milliseconds, as
measured from experiment begin time
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer blink detection; PyGaze algorithm \
will be used")
# # # # #
# PyGaze method
blinking = False
# loop until there is a blink
while not blinking:
# get newest sample
gazepos = self.sample()
# check if it's a valid sample
if not self.is_valid_sample(gazepos):
# get timestamp for possible blink start
t0 = clock.get_time()
# loop until a blink is determined, or a valid sample occurs
while not self.is_valid_sample(self.sample()):
# check if time has surpassed 150 ms
if clock.get_time()-t0 >= 150:
# return timestamp of blink start
return t0
def wait_for_fixation_end(self):
"""Returns time and gaze position when a fixation has ended;
function assumes that a 'fixation' has ended when a deviation of
more than self.pxfixtresh from the initial fixation position has
been detected (self.pxfixtresh is created in self.calibration,
based on self.fixtresh, a property defined in self.__init__)
arguments
None
returns
time, gazepos -- time is the starting time in milliseconds (from
expstart), gazepos is a (x,y) gaze position
tuple of the position from which the fixation
was initiated
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer fixation detection; \
PyGaze algorithm will be used")
# # # # #
# PyGaze method
# function assumes that a 'fixation' has ended when a deviation of more than fixtresh
# from the initial 'fixation' position has been detected
# get starting time and position
stime, spos = self.wait_for_fixation_start()
# loop until fixation has ended
while True:
# get new sample
npos = self.sample() # get newest sample
# check if sample is valid
if self.is_valid_sample(npos):
# check if sample deviates to much from starting position
if (npos[0]-spos[0])**2 + (npos[1]-spos[1])**2 > self.pxfixtresh**2: # Pythagoras
# break loop if deviation is too high
break
return clock.get_time(), spos
def wait_for_fixation_start(self):
"""Returns starting time and position when a fixation is started;
function assumes a 'fixation' has started when gaze position
remains reasonably stable (i.e. when most deviant samples are
within self.pxfixtresh) for five samples in a row (self.pxfixtresh
is created in self.calibration, based on self.fixtresh, a property
defined in self.__init__)
arguments
None
returns
time, gazepos -- time is the starting time in milliseconds (from
expstart), gazepos is a (x,y) gaze position
tuple of the position from which the fixation
was initiated
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a fixation start
# detection built into their API (only ending)
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer fixation detection; \
PyGaze algorithm will be used")
# # # # #
# PyGaze method
# function assumes a 'fixation' has started when gaze position
# remains reasonably stable for self.fixtimetresh
# get starting position
spos = self.sample()
while not self.is_valid_sample(spos):
spos = self.sample()
# get starting time
t0 = clock.get_time()
# wait for reasonably stable position
moving = True
while moving:
# get new sample
npos = self.sample()
# check if sample is valid
if self.is_valid_sample(npos):
# check if new sample is too far from starting position
if (npos[0]-spos[0])**2 + (npos[1]-spos[1])**2 > self.pxfixtresh**2: # Pythagoras
# if not, reset starting position and time
spos = copy.copy(npos)
t0 = clock.get_time()
# if new sample is close to starting sample
else:
# get timestamp
t1 = clock.get_time()
# check if fixation time threshold has been surpassed
if t1 - t0 >= self.fixtimetresh:
# return time and starting position
return t1, spos
def wait_for_saccade_end(self):
"""Returns ending time, starting and end position when a saccade is
ended; based on Dalmaijer et al. (2013) online saccade detection
algorithm
arguments
None
returns
endtime, startpos, endpos -- endtime in milliseconds (from
expbegintime); startpos and endpos
are (x,y) gaze position tuples
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer saccade detection; PyGaze \
algorithm will be used")
# # # # #
# PyGaze method
# get starting position (no blinks)
t0, spos = self.wait_for_saccade_start()
# get valid sample
prevpos = self.sample()
while not self.is_valid_sample(prevpos):
prevpos = self.sample()
# get starting time, intersample distance, and velocity
t1 = clock.get_time()
s = ((prevpos[0]-spos[0])**2 + (prevpos[1]-spos[1])**2)**0.5 # = intersample distance = speed in px/sample
v0 = s / (t1-t0)
# run until velocity and acceleration go below threshold
saccadic = True
while saccadic:
# get new sample
newpos = self.sample()
t1 = clock.get_time()
if self.is_valid_sample(newpos) and newpos != prevpos:
# calculate distance
s = ((newpos[0]-prevpos[0])**2 + (newpos[1]-prevpos[1])**2)**0.5 # = speed in pixels/sample
# calculate velocity
v1 = s / (t1-t0)
# calculate acceleration
a = (v1-v0) / (t1-t0) # acceleration in pixels/sample**2 (actually is v1-v0 / t1-t0; but t1-t0 = 1 sample)
# check if velocity and acceleration are below threshold
if v1 < self.pxspdtresh and (a > -1*self.pxacctresh and a < 0):
saccadic = False
epos = newpos[:]
etime = clock.get_time()
# update previous values
t0 = copy.copy(t1)
v0 = copy.copy(v1)
# udate previous sample
prevpos = newpos[:]
return etime, spos, epos
def wait_for_saccade_start(self):
"""Returns starting time and starting position when a saccade is
started; based on Dalmaijer et al. (2013) online saccade detection
algorithm
arguments
None
returns
endtime, startpos -- endtime in milliseconds (from expbegintime);
startpos is an (x,y) gaze position tuple
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer saccade detection; PyGaze \
algorithm will be used")
# # # # #
# PyGaze method
# get starting position (no blinks)
newpos = self.sample()
while not self.is_valid_sample(newpos):
newpos = self.sample()
# get starting time, position, intersampledistance, and velocity
t0 = clock.get_time()
prevpos = newpos[:]
s = 0
v0 = 0
# get samples
saccadic = False
while not saccadic:
# get new sample
newpos = self.sample()
t1 = clock.get_time()
if self.is_valid_sample(newpos) and newpos != prevpos:
# check if distance is larger than precision error
sx = newpos[0]-prevpos[0]; sy = newpos[1]-prevpos[1]
if (sx/self.pxdsttresh[0])**2 + (sy/self.pxdsttresh[1])**2 > self.weightdist: # weigthed distance: (sx/tx)**2 + (sy/ty)**2 > 1 means movement larger than RMS noise
# calculate distance
s = ((sx)**2 + (sy)**2)**0.5 # intersampledistance = speed in pixels/ms
# calculate velocity
v1 = s / (t1-t0)
# calculate acceleration
a = (v1-v0) / (t1-t0) # acceleration in pixels/ms**2
# check if either velocity or acceleration are above threshold values
if v1 > self.pxspdtresh or a > self.pxacctresh:
saccadic = True
spos = prevpos[:]
stime = clock.get_time()
# update previous values
t0 = copy.copy(t1)
v0 = copy.copy(v1)
# udate previous sample
prevpos = newpos[:]
return stime, spos
def is_valid_sample(self, gazepos):
"""Checks if the sample provided is valid, based on EyeTribe specific
criteria (for internal use)
arguments
gazepos -- a (x,y) gaze position tuple, as returned by
self.sample()
returns
valid -- a Boolean: True on a valid sample, False on
an invalid sample
"""
# return False if a sample is invalid
if gazepos == (None,None) or gazepos == (-1,-1):
return False
# in any other case, the sample is valid
return True
size = -999
print("ERROR in Pupil size: failed to obtain sample")
# remove potential None
if size == None:
x = -999
# send message
conn.send("success;s=%.4f" % (size))
# CLOSE
elif message == 'Close':
if tracker == None:
print('ERROR in Close: tracker was not initialized.')
conn.send('ERROR in Close: tracker was not initialized.')
else:
try:
tracker.close()
conn.send('success')
stopped = True
except:
print("ERROR in Close: failed to close connection.")
conn.send("ERROR in Close: failed to close connection.")
# UNKNOWN
else:
print("WARNING: message was not recognized!")
conn.send("WARNING: message was not recognized!")
print("original message: '%s'" % message)
# short pause
time.sleep(0.5)
class EyeTribeTracker(BaseEyeTracker):
"""A class for EyeTribeTracker objects"""
def __init__(self,
presenter,
screen_size,
screen_dist,
logfile,
eventdetection='pygaze',
saccade_velocity_threshold=35,
saccade_acceleration_threshold=9500,
blink_threshold=130):
"""Initializes the EyeTribeTracker object
arguments
window -- a Presenter instance
screen_size -- display size in cm
screen_dist -- distance to the display in cm
logfile -- logfile name (string value); note that this is the
name for the eye data log file (default = LOGFILE)
"""
# try to copy docstrings (but ignore it if it fails, as we do
# not need it for actual functioning of the code)
try:
copy_docstr(BaseEyeTracker, EyeTribeTracker)
except:
# we're not even going to show a warning, since the copied
# docstring is useful for code editors; these load the docs
# in a non-verbose manner, so warning messages would be lost
pass
# object properties
self.presenter = presenter
self.dispsize = presenter.window.size # display size in pixels
self.screensize = screen_size # display size in cm
self.screendist = screen_dist # distance to the display in cm
self.errorbeep = Sound(osc='saw', freq=100, length=100)
# output file properties
self.outputfile = logfile
# eye tracker properties
self.connected = False
self.recording = False
self.errdist = 2 # degrees; maximal error for drift correction
self.pxerrdist = 30 # initial error in pixels
self.maxtries = 100 # number of samples obtained before giving up (for obtaining accuracy and tracker distance information, as well as starting or stopping recording)
self.prevsample = (-1, -1)
self.prevps = -1
# event detection properties
self.fixtresh = 1.5 # degrees; maximal distance from fixation start (if gaze wanders beyond this, fixation has stopped)
self.fixtimetresh = 100 # milliseconds; amount of time gaze has to linger within self.fixtresh to be marked as a fixation
self.spdtresh = saccade_velocity_threshold # degrees per second; saccade velocity threshold
self.accthresh = saccade_acceleration_threshold # degrees per second**2; saccade acceleration threshold
self.blinkthresh = blink_threshold # milliseconds; blink detection threshold used in PyGaze method
self.eventdetection = eventdetection
self.set_detection_type(self.eventdetection)
self.weightdist = 10 # weighted distance, used for determining whether a movement is due to measurement error (1 is ok, higher is more conservative and will result in only larger saccades to be detected)
# connect to the tracker
self.eyetribe = EyeTribe(logfilename=logfile)
# get info on the sample rate
self.samplerate = self.eyetribe._samplefreq
self.sampletime = 1000.0 * self.eyetribe._intsampletime
# initiation report
self.log("pygaze initiation report start")
self.log("display resolution: %sx%s" %
(self.dispsize[0], self.dispsize[1]))
self.log("display size in cm: %sx%s" %
(self.screensize[0], self.screensize[1]))
self.log("samplerate: %.2f Hz" % self.samplerate)
self.log("sampletime: %.2f ms" % self.sampletime)
self.log("fixation threshold: %s degrees" % self.fixtresh)
self.log("speed threshold: %s degrees/second" % self.spdtresh)
self.log("acceleration threshold: %s degrees/second**2" %
self.accthresh)
self.log("pygaze initiation report end")
def calibrate(self, pre_calib_wait=500, calib_wait=1000):
"""Calibrates the eye tracking system
returns
success -- returns True if calibration succeeded, or False if
not; in addition a calibration log is added to the
log file and some properties are updated (i.e. the
thresholds for detection algorithms)
"""
def get_psychopy_pos(x, y):
return (x - self.dispsize[0] / 2), (y - self.dispsize[1] / 2)
# CALIBRATION
# determine the calibration points
calibpoints = []
margin = int(self.dispsize[1] / 10)
gap_x = int((self.dispsize[0] - 2 * margin) / 3)
gap_y = int((self.dispsize[1] - 2 * margin) / 3)
for x in range(4):
for y in range(4):
calibpoints.append((margin + gap_x * x, margin + gap_y * y))
random.shuffle(calibpoints) # shuffle two lists together
# show a message
black_bg = visual.Rect(self.presenter.window,
width=2.1,
height=2.1,
fillColor='black')
self.presenter.show_instructions(
'Press space to calibrate\n\nFollow circles with your eyes',
other_stim=[black_bg],
next_instr_text=None)
quited = False
# Pause the processing of samples during the calibration.
# self.eyetribe._pause_sample_processing()
# run until the user is statisfied, or quits
calibrated = False
calibresult = None
while not quited and not calibrated:
# Clear the existing calibration.
if self.eyetribe._tracker.get_iscalibrated():
self.eyetribe._lock.acquire(True)
self.eyetribe.calibration.clear()
self.eyetribe._lock.release()
# Wait for a bit.
clock.pause(1500)
# start a new calibration
if not self.eyetribe._tracker.get_iscalibrating():
self.eyetribe._lock.acquire(True)
self.eyetribe.calibration.start(pointcount=len(calibpoints))
self.eyetribe._lock.release()
# loop through calibration points
for cpos in calibpoints:
# Check whether the calibration is already done.
# (Not sure how or why, but for some reason some data
# can persist between calbrations, and the tracker will
# simply stop allowing further pointstart requests.)
if self.eyetribe._tracker.get_iscalibrated():
break
# Draw a calibration target.
point = get_psychopy_pos(cpos[0], cpos[1])
self.draw_calibration_target(point[0], point[1], black_bg)
# wait for a bit to allow participant to start looking at
# the calibration point
clock.pause(pre_calib_wait)
# start calibration of point
self.eyetribe._lock.acquire(True)
self.eyetribe.calibration.pointstart(cpos[0], cpos[1])
self.eyetribe._lock.release()
# wait for a second
clock.pause(calib_wait)
# stop calibration of this point
self.eyetribe._lock.acquire(True)
self.eyetribe.calibration.pointend()
self.eyetribe._lock.release()
# empty display
self.presenter.draw_stimuli_for_duration([black_bg], duration=None)
# allow for a bit of calculation time
# (this is waaaaaay too much)
clock.pause(1000)
def show_calibration(self):
def get_psychopy_pos(x, y):
return (x - self.dispsize[0] / 2), (y - self.dispsize[1] / 2)
# get the calibration result
self.eyetribe._lock.acquire(True)
calibresult = self.eyetribe._tracker.get_calibresult()
self.eyetribe._lock.release()
# results
# clear the screen
# self.screen.clear()
# draw results for each point
if type(calibresult) != dict:
stimuli = [
visual.TextStim(self.presenter.window,
text='Calibration failed.')
]
else:
stimuli = []
for p in calibresult['calibpoints']:
# only draw the point if data was obtained
if p['state'] > 0:
# draw the mean error
# self.screen.draw_circle(colour=(252,233,79),
# pos=(p['cpx'],p['cpy']), r=p['mepix'], pw=0,
# fill=True)
line = visual.Line(
win=self.presenter.window,
units='pix',
lineWidth=0.5,
start=get_psychopy_pos(p['cpx'], p['cpy']),
end=get_psychopy_pos(p['mecpx'], p['mecpy']))
# draw the point
point = visual.Circle(self.presenter.window,
units='pix',
lineWidth=1,
lineColor='white',
edges=128,
radius=3,
opacity=1,
pos=get_psychopy_pos(
p['cpx'], p['cpy']))
# draw the estimated point
est_point = visual.Circle(self.presenter.window,
units='pix',
lineWidth=1,
lineColor='red',
edges=128,
radius=3,
opacity=1,
pos=get_psychopy_pos(
p['mecpx'], p['mecpy']))
# annotate accuracy
text = visual.TextStim(self.presenter.window,
text='%.2f' % p['acd'],
pos=get_psychopy_pos(
p['cpx'] + 15, p['cpy'] + 15),
height=0.07)
stimuli += [text, line, point, est_point]
# if no data was obtained, draw the point in red
else:
stimuli.append(
visual.Circle(self.presenter.window,
units='pix',
lineWidth=1,
lineColor='red',
edges=4,
radius=3,
opacity=1,
pos=get_psychopy_pos(p['cpx'],
p['cpy'])))
# draw result
if calibresult['result']:
stimuli.append(
visual.TextStim(self.presenter.window,
text='Calibration successful',
color='#84ff84',
pos=(0, -0.4),
height=0.05))
else:
stimuli.append(
visual.TextStim(self.presenter.window,
text='Calibration failed',
color='red',
pos=(0, -0.4),
height=0.05))
# draw average accuracy
stimuli.append(
visual.TextStim(self.presenter.window,
pos=(0, -0.5),
height=0.08,
text='Average error = %.2f degrees' %
(calibresult['deg'])))
# show the results
self.presenter.draw_stimuli_for_response(stimuli,
response_keys=['space'])
# NOISE CALIBRATION
# get all error estimates (pixels)
var = []
for p in calibresult['calibpoints']:
# only draw the point if data was obtained
if p['state'] > 0:
var.append(p['mepix'])
noise = sum(var) / float(len(var))
self.pxdsttresh = (noise, noise)
# AFTERMATH
# store some variables
pixpercm = (self.dispsize[0] / float(self.screensize[0]) +
self.dispsize[1] / float(self.screensize[1])) / 2
screendist = self.screendist
# calculate thresholds based on tracker settings
self.accuracy = ((calibresult['Ldeg'], calibresult['Ldeg']),
(calibresult['Rdeg'], calibresult['Rdeg']))
self.pxerrdist = deg2pix(screendist, self.errdist, pixpercm)
self.pxfixtresh = deg2pix(screendist, self.fixtresh, pixpercm)
self.pxaccuracy = ((deg2pix(screendist, self.accuracy[0][0], pixpercm),
deg2pix(screendist, self.accuracy[0][1],
pixpercm)),
(deg2pix(screendist, self.accuracy[1][0], pixpercm),
deg2pix(screendist, self.accuracy[1][1],
pixpercm)))
self.pxspdtresh = deg2pix(screendist, self.spdtresh / 1000.0,
pixpercm) # in pixels per millisecond
self.pxacctresh = deg2pix(screendist, self.accthresh / 1000.0,
pixpercm) # in pixels per millisecond**2
# calibration report
self.log("pygaze calibration report start")
self.log("accuracy (degrees): LX=%s, LY=%s, RX=%s, RY=%s" %
(self.accuracy[0][0], self.accuracy[0][1],
self.accuracy[1][0], self.accuracy[1][1]))
self.log("accuracy (in pixels): LX=%s, LY=%s, RX=%s, RY=%s" %
(self.pxaccuracy[0][0], self.pxaccuracy[0][1],
self.pxaccuracy[1][0], self.pxaccuracy[1][1]))
self.log("precision (RMS noise in pixels): X=%s, Y=%s" %
(self.pxdsttresh[0], self.pxdsttresh[1]))
self.log("distance between participant and display: %s cm" %
screendist)
self.log("fixation threshold: %s pixels" % self.pxfixtresh)
self.log("speed threshold: %s pixels/ms" % self.pxspdtresh)
self.log("acceleration threshold: %s pixels/ms**2" % self.pxacctresh)
self.log("pygaze calibration report end")
return True
def close(self):
"""Neatly close connection to tracker
arguments
None
returns
Nothing -- saves data and sets self.connected to False
"""
# close connection
self.eyetribe.close()
self.connected = False
def connected(self):
"""Checks if the tracker is connected
arguments
None
returns
connected -- True if connection is established, False if not;
sets self.connected to the same value
"""
res = self.eyetribe._tracker.get_trackerstate()
if res == 0:
self.connected = True
else:
self.connected = False
return self.connected
def drift_correction(self, pos=None, fix_triggered=True):
"""Performs a drift check
arguments
None
keyword arguments
pos -- (x, y) position of the fixation dot or None for
a central fixation (default = None)
fix_triggered -- Boolean indicating if drift check should be
performed based on gaze position (fix_triggered
= True) or on spacepress (fix_triggered =
False) (default = False)
returns
checked -- Boolaan indicating if drift check is ok (True)
or not (False); or calls self.calibrate if 'q'
or 'escape' is pressed
"""
if pos is None:
pos = self.dispsize[0] / 2, self.dispsize[1] / 2
if fix_triggered:
return self.fix_triggered_drift_correction(pos)
raise RuntimeError('Don\'t trigger drift correction by key alright?')
# self.draw_drift_correction_target(pos[0], pos[1])
# pressed = False
# while not pressed:
# pressed, presstime = self.kb.get_key()
# if pressed:
# if pressed == 'escape' or pressed == 'q':
# print("libeyetribe.EyeTribeTracker.drift_correction: 'q' or 'escape' pressed")
# return self.calibrate()
# gazepos = self.sample()
# if ((gazepos[0] - pos[0]) ** 2 + (gazepos[1] - pos[1]) ** 2) ** 0.5 < self.pxerrdist:
# return True
# else:
# self.errorbeep.play()
# return False
def draw_drift_correction_target(self, x, y, bg=None):
"""
Draws the drift-correction target.
arguments
x -- The X coordinate
y -- The Y coordinate
"""
center = visual.Circle(self.presenter.window,
units='pix',
lineWidth=0,
fillColor='white',
edges=128,
radius=2,
pos=(x, y))
border = visual.Circle(self.presenter.window,
units='pix',
lineWidth=0,
fillColor='white',
edges=128,
radius=4,
opacity=0.5,
pos=(x, y))
out_border = visual.Circle(self.presenter.window,
units='pix',
lineWidth=3,
fillColor='white',
edges=128,
radius=22,
opacity=0.1,
pos=(x, y))
stims = [center, border, out_border
] if bg is None else [bg, center, border, out_border]
self.presenter.draw_stimuli_for_duration(stims, duration=None)
def draw_calibration_target(self, x, y, bg=None):
self.draw_drift_correction_target(x, y, bg)
def fix_triggered_drift_correction(self,
pos=None,
min_samples=10,
max_dev=60,
reset_threshold=30):
"""Performs a fixation triggered drift correction by collecting
a number of samples and calculating the average distance from the
fixation position
arguments
None
keyword arguments
pos -- (x, y) position of the fixation dot or None for
a central fixation (default = None)
min_samples -- minimal amount of samples after which an
average deviation is calculated (default = 10)
max_dev -- maximal deviation from fixation in pixels
(default = 60)
reset_threshold -- if the horizontal or vertical distance in
pixels between two consecutive samples is
larger than this threshold, the sample
collection is reset (default = 30)
returns
checked -- Boolaan indicating if drift check is ok (True)
or not (False); or calls self.calibrate if 'q'
or 'escape' is pressed
"""
if pos is None:
pos = self.dispsize[0] / 2, self.dispsize[1] / 2
self.draw_drift_correction_target(pos[0], pos[1])
# loop until we have sufficient samples
lx = []
ly = []
while len(lx) < min_samples:
# pressing escape enters the calibration screen
# if self.kb.get_key()[0] in ['escape', 'q']:
# print("libeyetribe.EyeTribeTracker.fix_triggered_drift_correction: 'q' or 'escape' pressed")
# return self.calibrate()
# collect a sample
x, y = self.sample()
if len(lx) == 0 or x != lx[-1] or y != ly[-1]:
# if present sample deviates too much from previous sample, reset counting
if len(lx) > 0 and (abs(x - lx[-1]) > reset_threshold
or abs(y - ly[-1]) > reset_threshold):
lx = []
ly = []
# collect samples
else:
lx.append(x)
ly.append(y)
if len(lx) == min_samples:
avg_x = sum(lx) / len(lx)
avg_y = sum(ly) / len(ly)
d = ((avg_x - pos[0])**2 + (avg_y - pos[1])**2)**0.5
if d < max_dev:
return True
else:
lx = []
ly = []
def log(self, msg):
"""Writes a message to the log file
arguments
ms -- a string to include in the log file
returns
Nothing -- uses native log function of iViewX to include a line
in the log file
"""
self.eyetribe.log_message(msg)
def prepare_drift_correction(self, pos):
"""Not supported for EyeTribeTracker (yet)"""
print("function not supported yet")
def pupil_size(self):
"""Return pupil size
arguments
None
returns
pupil size -- returns pupil diameter for the eye that is currently
being tracked (as specified by self.eye_used) or -1
when no data is obtainable
"""
# get newest pupil size
ps = self.eyetribe.pupil_size()
# invalid data
if ps is None:
return -1
# check if the new pupil size is the same as the previous
if ps != self.prevps:
# update the pupil size
self.prevps = copy.copy(ps)
return self.prevps
def sample(self):
"""Returns newest available gaze position
arguments
None
returns
sample -- an (x,y) tuple or a (-1,-1) on an error
"""
# get newest sample
s = self.eyetribe.sample()
# invalid data
if s == (None, None):
return -1, -1
# check if the new sample is the same as the previous
if s != self.prevsample:
# update the current sample
self.prevsample = copy.copy(s)
return self.prevsample
def send_command(self, cmd):
"""Sends a command to the eye tracker
arguments
cmd -- the command to be sent to the EyeTribe, which should
be a list with the following information:
[category, request, values]
returns
Nothing
"""
self.eyetribe._connection.request(cmd)
def start_recording(self):
"""Starts recording eye position
arguments
None
returns
Nothing -- sets self.recording to True when recording is
successfully started
"""
self.eyetribe.start_recording()
self.recording = True
def stop_recording(self):
"""Stop recording eye position
arguments
None
returns
Nothing -- sets self.recording to False when recording is
successfully started
"""
self.eyetribe.stop_recording()
self.recording = False
def set_detection_type(self, eventdetection):
"""Set the event detection type to either PyGaze algorithms, or
native algorithms as provided by the manufacturer (only if
available: detection type will default to PyGaze if no native
functions are available)
arguments
eventdetection -- a string indicating which detection type
should be employed: either 'pygaze' for
PyGaze event detection algorithms or
'native' for manufacturers algorithms (only
if available; will default to 'pygaze' if no
native event detection is available)
returns -- detection type for saccades, fixations and
blinks in a tuple, e.g.
('pygaze','native','native') when 'native'
was passed, but native detection was not
available for saccade detection
"""
if eventdetection in ['pygaze', 'native']:
self.eventdetection = eventdetection
return 'pygaze', 'pygaze', 'pygaze'
def wait_for_event(self, event):
"""Waits for event
arguments
event -- an integer event code, one of the following:
3 = STARTBLINK
4 = ENDBLINK
5 = STARTSACC
6 = ENDSACC
7 = STARTFIX
8 = ENDFIX
returns
outcome -- a self.wait_for_* method is called, depending on the
specified event; the return values of corresponding
method are returned
"""
if event == 5:
outcome = self.wait_for_saccade_start()
elif event == 6:
outcome = self.wait_for_saccade_end()
elif event == 7:
outcome = self.wait_for_fixation_start()
elif event == 8:
outcome = self.wait_for_fixation_end()
elif event == 3:
outcome = self.wait_for_blink_start()
elif event == 4:
outcome = self.wait_for_blink_end()
else:
raise Exception(
"Error in libsmi.SMItracker.wait_for_event: eventcode %s is not supported"
% event)
return outcome
def wait_for_blink_end(self):
"""Waits for a blink end and returns the blink ending time
arguments
None
returns
timestamp -- blink ending time in milliseconds, as
measured from experiment begin time
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print(
"WARNING! 'native' event detection has been selected, "
"but EyeTribe does not offer blink detection; PyGaze algorithm "
"will be used")
# # # # #
# PyGaze method
blinking = True
# loop while there is a blink
while blinking:
# get newest sample
gazepos = self.sample()
# check if it's valid
if self.is_valid_sample(gazepos):
# if it is a valid sample, blinking has stopped
blinking = False
# return timestamp of blink end
return clock.get_time()
def wait_for_blink_start(self):
"""Waits for a blink start and returns the blink starting time
arguments
None
returns
timestamp -- blink starting time in milliseconds, as
measured from experiment begin time
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print(
"WARNING! 'native' event detection has been selected, "
"but EyeTribe does not offer blink detection; PyGaze algorithm "
"will be used")
# # # # #
# PyGaze method
blinking = False
# loop until there is a blink
while not blinking:
# get newest sample
gazepos = self.sample()
# check if it's a valid sample
if not self.is_valid_sample(gazepos):
# get timestamp for possible blink start
t0 = clock.get_time()
# loop until a blink is determined, or a valid sample occurs
while not self.is_valid_sample(self.sample()):
# check if time has surpassed BLINKTHRESH
if clock.get_time() - t0 >= self.blinkthresh:
# return timestamp of blink start
return t0
def wait_for_fixation_end(self):
"""Returns time and gaze position when a fixation has ended;
function assumes that a 'fixation' has ended when a deviation of
more than self.pxfixtresh from the initial fixation position has
been detected (self.pxfixtresh is created in self.calibration,
based on self.fixtresh, a property defined in self.__init__)
arguments
None
returns
time, gazepos -- time is the starting time in milliseconds (from
expstart), gazepos is a (x,y) gaze position
tuple of the position from which the fixation
was initiated
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer fixation detection; \
PyGaze algorithm will be used")
# # # # #
# PyGaze method
# function assumes that a 'fixation' has ended when a deviation of more than fixtresh
# from the initial 'fixation' position has been detected
# get starting time and position
stime, spos = self.wait_for_fixation_start()
# loop until fixation has ended
while True:
# get new sample
npos = self.sample() # get newest sample
# check if sample is valid
if self.is_valid_sample(npos):
# check if sample deviates to much from starting position
if (npos[0] - spos[0])**2 + (
npos[1] -
spos[1])**2 > self.pxfixtresh**2: # Pythagoras
# break loop if deviation is too high
break
return clock.get_time(), spos
def wait_for_fixation_start(self):
"""Returns starting time and position when a fixation is started;
function assumes a 'fixation' has started when gaze position
remains reasonably stable (i.e. when most deviant samples are
within self.pxfixtresh) for five samples in a row (self.pxfixtresh
is created in self.calibration, based on self.fixtresh, a property
defined in self.__init__)
arguments
None
returns
time, gazepos -- time is the starting time in milliseconds (from
expstart), gazepos is a (x,y) gaze position
tuple of the position from which the fixation
was initiated
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a fixation start
# detection built into their API (only ending)
print("WARNING! 'native' event detection has been selected, \
but EyeTribe does not offer fixation detection; \
PyGaze algorithm will be used")
# # # # #
# PyGaze method
# function assumes a 'fixation' has started when gaze position
# remains reasonably stable for self.fixtimetresh
# get starting position
spos = self.sample()
while not self.is_valid_sample(spos):
spos = self.sample()
# get starting time
t0 = clock.get_time()
# wait for reasonably stable position
moving = True
while moving:
# get new sample
npos = self.sample()
# check if sample is valid
if self.is_valid_sample(npos):
# check if new sample is too far from starting position
if (npos[0] - spos[0])**2 + (
npos[1] -
spos[1])**2 > self.pxfixtresh**2: # Pythagoras
# if not, reset starting position and time
spos = copy.copy(npos)
t0 = clock.get_time()
# if new sample is close to starting sample
else:
# get timestamp
t1 = clock.get_time()
# check if fixation time threshold has been surpassed
if t1 - t0 >= self.fixtimetresh:
# return time and starting position
return t1, spos
def wait_for_saccade_end(self):
"""Returns ending time, starting and end position when a saccade is
ended; based on Dalmaijer et al. (2013) online saccade detection
algorithm
arguments
None
returns
endtime, startpos, endpos -- endtime in milliseconds (from
expbegintime); startpos and endpos
are (x,y) gaze position tuples
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, "
"but EyeTribe does not offer saccade detection; PyGaze "
"algorithm will be used")
# # # # #
# PyGaze method
# get starting position (no blinks)
t0, spos = self.wait_for_saccade_start()
# get valid sample
prevpos = self.sample()
while not self.is_valid_sample(prevpos):
prevpos = self.sample()
# get starting time, intersample distance, and velocity
t1 = clock.get_time()
s = ((prevpos[0] - spos[0])**2 + (prevpos[1] - spos[1])**
2)**0.5 # = intersample distance = speed in px/sample
v0 = s / (t1 - t0)
# run until velocity and acceleration go below threshold
saccadic = True
while saccadic:
# get new sample
newpos = self.sample()
t1 = clock.get_time()
if self.is_valid_sample(newpos) and newpos != prevpos:
# calculate distance
s = ((newpos[0] - prevpos[0])**2 + (newpos[1] - prevpos[1])**
2)**0.5 # = speed in pixels/sample
# calculate velocity
v1 = s / (t1 - t0)
# calculate acceleration
a = (v1 - v0) / (
t1 - t0
) # acceleration in pixels/sample**2 (actually is v1-v0 / t1-t0; but t1-t0 = 1 sample)
# check if velocity and acceleration are below threshold
if v1 < self.pxspdtresh and (a > -1 * self.pxacctresh
and a < 0):
saccadic = False
epos = newpos[:]
etime = clock.get_time()
# update previous values
t0 = copy.copy(t1)
v0 = copy.copy(v1)
# udate previous sample
prevpos = newpos[:]
return etime, spos, epos
def wait_for_saccade_start(self):
"""Returns starting time and starting position when a saccade is
started; based on Dalmaijer et al. (2013) online saccade detection
algorithm
arguments
None
returns
endtime, startpos -- endtime in milliseconds (from expbegintime);
startpos is an (x,y) gaze position tuple
"""
# # # # #
# EyeTribe method
if self.eventdetection == 'native':
# print warning, since EyeTribe does not have a blink detection
# built into their API
print("WARNING! 'native' event detection has been selected, "
"but EyeTribe does not offer saccade detection; PyGaze "
"algorithm will be used")
# # # # #
# PyGaze method
# get starting position (no blinks)
newpos = self.sample()
while not self.is_valid_sample(newpos):
newpos = self.sample()
# get starting time, position, intersampledistance, and velocity
t0 = clock.get_time()
prevpos = newpos[:]
s = 0
v0 = 0
# get samples
saccadic = False
while not saccadic:
# get new sample
newpos = self.sample()
t1 = clock.get_time()
if self.is_valid_sample(newpos) and newpos != prevpos:
# check if distance is larger than precision error
sx = newpos[0] - prevpos[0]
sy = newpos[1] - prevpos[1]
if (sx / self.pxdsttresh[0])**2 + (
sy / self.pxdsttresh[1]
)**2 > self.weightdist: # weigthed distance: (sx/tx)**2 + (sy/ty)**2 > 1 means movement larger than RMS noise
# calculate distance
s = ((sx)**2 + (sy)**
2)**0.5 # intersampledistance = speed in pixels/ms
# calculate velocity
v1 = s / (t1 - t0)
# calculate acceleration
a = (v1 - v0) / (t1 - t0) # acceleration in pixels/ms**2
# check if either velocity or acceleration are above threshold values
if v1 > self.pxspdtresh or a > self.pxacctresh:
saccadic = True
spos = prevpos[:]
stime = clock.get_time()
# update previous values
t0 = copy.copy(t1)
v0 = copy.copy(v1)
# udate previous sample
prevpos = newpos[:]
return stime, spos
def is_valid_sample(self, gazepos):
"""Checks if the sample provided is valid, based on EyeTribe specific
criteria (for internal use)
arguments
gazepos -- a (x,y) gaze position tuple, as returned by
self.sample()
returns
valid -- a Boolean: True on a valid sample, False on
an invalid sample
"""
# return False if a sample is invalid
if gazepos == (None, None) or gazepos == (-1, -1):
return False
# in any other case, the sample is valid
return True