Visual Stimuli with different offsets

[Cognitology]

Hi David,
Canvas drawing operations are not necessarily terribly slow: you can declare
an extra display (I call it a buffered display), draw everything at a moment
in time you can afford to be slow, and then swap the buffered display to the
current display. I'm not sure if the terminology is still correct, but I
have been well able to make things like pattern masks in which a 100x100
image was drawn with each of the 10,000 pixels being randomly black or white
and switching this image 20 times every 10 ms (the trick then is to draw the
whole thing at the beginning of the trial, then grab 100x100 pixels of the
buffered display and dump them on the current one. It can work, but I agree
it's not easy.

On the topic of critical timing and inline code:
I found out that it costs, on my (quite fast) pc, the simple debug.print "a"
takes about 0.47 ms. However,
For I = 1:10000
    Debug.print "a"
Next I

Takes about 7 seconds. I took this to mean that the simple act of loading a
value into I takes about 0.2 ms as well. The other value (of 0.47 ms) I got
was by logging the time to do
Debug.print "a"
Debug.print "a"
...
X 10, x 100, x 1000, x10000 times.

So, this suggests that our common advice of "if you can do it without inline
code, do that instead" is probably best. 
Beware! :)
Best,
Michiel


-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf
Of David McFarlane
Sent: 15. March 2013 17:09
To: e-prime at googlegroups.com
Subject: Re: Visual Stimuli with different offsets

Hmm.  In short, you need some way to clear only one of the stimuli at a
specified time after first presenting both stimuli.  Let's see...  First,
set the Duration of the dual stimulus to the shorter Duration.  Then you
could simply replace that with an object that presents only one of those
stimuli, with its Duration set to the time remaining for that stimulus.  Or
use an object with a judiciously set combination of Frame Size & Position
and transparent BackStyle to overwrite just the one stimulus.  Or use
SlideVisualStim.Clear in inline code to clear the one stimulus.  In any
case, you then do something to take up the remaining time for the
longer-duration stimulus.  Anybody have a beter idea?

If you want draw your own stimuli in E-Prime then you may use the Canvas
object to draw whatever you like, see that topic in the E-Basic Help
facility.  This will require some inline coding.  Please note that Canvas
drawing operations are *far* too slow for anything terribly complex, but
still good enough for modest use.

-----
David McFarlane
E-Prime training
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster)

/----
Stock reminder:  1) I do not work for PST.  2) PST's trained staff take any
and all questions at http://support.pstnet.com/e%2Dprime/support/login.asp ,
and they strive to respond to all requests in 24-48 hours, so make full use
of it.  3) In addition, PST offers several instructional videos on their
YouTube channel (http://www.youtube.com/user/PSTNET ).  4) If you do get an
answer from PST staff, please extend the courtesy of posting their reply
back here for the sake of others.
\----


At 3/15/2013 10:33 AM Friday, kayh wrote:
>I am new to e-prime and I am having some trouble figuring out how to 
>change duration times.
>Currently, I need to be able to have two stimuli on the same page have 
>different durations. While I know you can change duration times for 
>full pages, I have not been able to change the duration of one stimuli 
>without changing them all.
>Does any body have any solutions for this?
>
>Background information: I am trying to have two stimuli (circles) have 
>the same onset time, but their offset time be slightly different. Also, 
>is there anyway to create shapes in e-prime? or do i have to import 
>images?
>
>Any help would be greatly appreciated!! Thanks!!

--
You received this message because you are subscribed to the Google Groups
"E-Prime" group.
To unsubscribe from this group and stop receiving emails from it, send an
email to e-prime+unsubscribe at googlegroups.com.
To post to this group, send email to e-prime at googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.



-- 
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To unsubscribe from this group and stop receiving emails from it, send an email to e-prime+unsubscribe at googlegroups.com.
To post to this group, send email to e-prime at googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.