[visionegg] Re: Ghosting of previous stimulus (was: Advice on using Presentation for sequential stimulus.)

Hi Simeon,

Given that it doesn't happen in windowed mode, only fullscreen mode, it does sound like an OpenGL driver issue. As a workaround, you can make a "frameless" window the same size as your desktop, and it will act, for all intents and purposes, like fullscreen. in fact, on Windows, this is a good way to go, because you can set the refresh rate and so on for your display using the standard tools and then keep it exactly that way for your experiments.

As a test that the FixationSpot is not getting re-drawn, just put a print statement in its draw routine to verify what's happening.

Cheers!
Andrew

On Aug 24, 2005, at 9:11 AM, Simeon Fitch wrote:

Andrew,

I definitely want to follow up later with some ideas on how to add
simplified support for sequential stimuli, as you've described below
(I've a pressing deadline right now). My current approach (as I
previously described) has run into a problem when in full screen mode
I'm hoping is related to my neglecting a setting or something, but I'm
not quite sure how to start tracking it down.

In my experiment, I first show the Vision Egg provided FixationSpot,
then display three different "frames" of a dot lattice mask (@50ms
each), and then the main stimulus. In between each of the three mask
frames, the FixationSpot re-appears on the screen! It's almost as if
the FixationSpot is being redrawn, or it exists in a back buffer
that's not getting cleared, or something similar.

This problem does *not* happen when in windowed mode, so it could just
be a OpenGL driver bug (OpenGL 1.3 ATI-1.4.6, ATI Radeon 9200 OpenGL
Engine)

Any tips on how to debug this would be appreciated.

Regards,

Simeon

On 8/22/05, Andrew Straw <astraw@xxxxxxxxxxx> wrote:

<snip>


This is an area where improvements could be made, I think. I'm somewhat
inspired by the "trial strings" of PsyScript/RSVP [1]. Although I've
never worked with it, it seems to describe the time-course of entire
experiments in strings of a few characters. So, some kind of simplified
experiment description is an interesting possibility. I assume such
simplification would come at the expense of assumptions about what
experiments people want to do, but perhaps those assumptions are met
enough of the time to justify implementing some system like this.

[1]: A description of the "do trial" command in PsyScript:
http://www.maccs.mq.edu.au/~tim/psyscript/docs/trials/ intro_to_do_trial.html


Simeon Fitch wrote: 
<snip>

# Main experimentation loop
for trial in conditions:
    lattice.setTrial(trial)

    fixationPres.go()
    maskPres.go()
    latticePres.go()
    responsePres.go()

dataFileWriter.writerow(trial.values()) 
--
Simeon H.K. Fitch, Owner
Mustard Seed Software
http://www.mseedsoft.com/
======================================
The Vision Egg mailing list
Archives: http://www.freelists.org/archives/visionegg
Website: http://www.visionegg.org/mailinglist.html



======================================
The Vision Egg mailing list
Archives: http://www.freelists.org/archives/visionegg
Website: http://www.visionegg.org/mailinglist.html

Other related posts: