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Thread: Display a constant background image?

  1. #1
    Join Date
    Nov 2005
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    Display a constant background image?

    [edited from support email]
    I am trying to figure out how to keep a picture on the screen throughout the time that the subject is answering.
    Last edited by jarvis24; 10-02-2006 at 09:10 PM.

  2. #2
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    There is the inevitable gap between trials. You can shorten that though by using a shorter trial interval in the options of your style file (e.g., 100ms instead of 1000ms). You don't want to go much shorter than that though because DirectRT uses that time to prepare the trials. You can check your log data file to see the typical time it's taking DirectRT to prepare each trial (see the "load time" column). So long as your trial interval exceeds the maximum values in there you should be ok.
    Last edited by jarvis24; 10-02-2006 at 09:10 PM.

  3. #3
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    Sep 2006
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    2

    constant background; An answer with a question

    The way I do it is my putting by making one long line. As usual you will have the block-trial-bgr-wgr-style-loc-time, the trick is to set the first stimulus to have 0 under time and then repeat the stimulus-loc-time for all the stimuli you would like to present in the same line. Also remember that all the stimuli following the first background image should have a loc of 0,0,0. Attached is an example.
    Attached Files Attached Files

  4. #4
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    Yes, that will work. But for times when you have a 100 trials (or 1000!), that's a really nasty way to work with it. I will have to work something out to make it possible across separate trials.

  5. #5
    Join Date
    Sep 2007
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    Development of constant background image syntax?

    Hi-

    Did anything ever develop where a background image could be maintained on screen across all trials? I'm working on an experiment that is presenting word stimuli between two vertical bars, and it would be good if those bars were simply constant (instead of re-drawn on a trial-by-trial basis).

    clint

  6. #6
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    Nope, not yet, not aside from using shorter trial intervals for shorter blanking.

  7. #7
    Join Date
    Dec 2007
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    11

    this would be a very nice feature to have

    We use the fixation cross as a baseline condition and it would save study time if we could use the trial interval as a part of that period.

    The abilty to display either text (we could use a "+") and/or an image would work.

    On this topic, is the timing of the trial interval as precise as the presentation timing?
    Last edited by lncs; 12-07-2007 at 03:21 PM.

  8. #8
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    Yes, the precision is the same. We definitely have this one (constant or carry-over background) on our to-do list for the next major version.

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