Adjust Stimulus Movement Speed on Screen

Coding
1

I’m practicing with moving stimuli during a task. I have a countdown timer, a progress bar, and a circle that makes a loop around the countdown timer. My problem is that the circle does not make a complete loop before the timer is finished, and I don’t know how to speed this up. Is there a better way than what I have? Here is what I’ve been doing:

from __future__ import division
from psychopy import locale_setup, visual, core, event, data, gui
import os, platform, math, shlex
import subprocess as subp

#Set window and remove mouse during experiment:
win = visual.Window(fullscr=True, pos=(0,0), units="norm", color = "Black")
event.Mouse(visible=False)

#Determine Monitor Resolution:
if platform.system() == "Windows":
    from win32api import GetSystemMetrics
    width, height = GetSystemMetrics(0), GetSystemMetrics(1)
elif platform.system() == "Darwin":
    p = subp.Popen(shlex.split("system_profiler SPDisplaysDataType"), stdout=subp.PIPE)
    output = subp.check_output(('grep', 'Resolution'), stdin=p.stdout)
    width, height = [int(x.strip(' ')) for x in output.split(':')[-1].split(' x ')]
    
#Create stimuli:
text = visual.TextStim(win, text=' ', pos=(0,0), height = 0.5, color="White")
circle = visual.Circle(win, radius=0.05, pos = (0,0.5), fillColor="Yellow")
prog_bar = visual.Rect(win, pos=(-1.0, -0.8), fillColor="White")    

#Set varaibles
cdTime = 5.0 
speed = 4/cdTime
pi = math.pi
radius = text.boundingBox[1]/height + 0.1

#Set timer:
timer = core.Clock()

timer.reset()
time_start = timer.getTime()
countdownTimer = core.CountdownTimer(cdTime)

while countdownTimer.getTime() > 0.0:
    thesekeys = event.getKeys(keyList=["escape"])
    if len(thesekeys):
        break
        
    text.text= int(round(math.ceil(countdownTimer.getTime()),0))
    prog_bar.size = (((cdTime-countdownTimer.getTime())*2)*speed, 0.3) #Multiply by 2 to move progress bar in 1 direction, multiply by speed for progress to finish when timer finishes
    circle.pos = (radius*math.cos(cdTime-countdownTimer.getTime()+0.1), radius*math.sin(cdTime-countdownTimer.getTime())+0.1)
    text.draw()
    circle.draw()
    prog_bar.draw()
    
    win.flip()
time_end = timer.getTime()

print "Length of countdown: %s" %(time_end - time_start)

#Finish
win.close()
core.quit()
2

It’s a trig issue. What you want is for the cos and sin values to be the same when the countdown timer is at 5 seconds and at 0 seconds. Right now that’s not the case. At t=0s, when countdowntimer.gettime returns 5, you’re getting radiuscos(0+.1). At t=5s, when gettime returns 0, you’re getting radiuscos(5+.1). If you look at a graph for cos(x), when x=.1 and x=5.1, you don’t get the same value. You want it to be more like at t=0s you’re getting cos(0) and at t=5s you’re getting cos(2pi)

Here’s a replacement for the circle.pos line that should work better:

circle.pos = (radius*math.cos(((cdTime-countdownTimer.getTime())/cdTime)*2*pi), radius*math.sin(((cdTime-countdownTimer.getTime())/cdTime)*2*pi))
1 Like
3

Thanks for your response. That fixed my issue.

4

No problem. Make sure to tick ‘solved’ on this thread, it helps the developer(s) keep track of what’s still an open issue.

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