creating an oscillating bar using an inline element

[lml1934 at gmail.com]

Another option. Create an animation in Final Cut save as an .avi file and run as a movie. Much easier for placement on the screen.
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-----Original Message-----
From: "Vinson, David" <d.vinson at ucl.ac.uk>
Sender: e-prime at googlegroups.com
Date: Sun, 29 Jan 2012 12:58:58 
To: e-prime at googlegroups.com<e-prime at googlegroups.com>
Reply-To: e-prime at googlegroups.com
Subject: RE: creating an oscillating bar using an inline element

Hi BeckyL,

It looks like your main assumption is correct - holding y1 constant rather than varying it along with x1 should produce horizontal motion in the Simple Animation example.   If it works on the first trial it's not a complete failure but may have something to do with changes in values from one trial to the next.

My guess is that there's something amiss with your treatment of y1 outside of the assignment to a constant value.  Perhaps the exit condition is never met:  as in the code below, y1 will never reach 30 if you get rid of (y1 = y1 - 1).  So it will run fine, until x1 reaches the edge of the screen in which case it will either crash (display of negative values for x may break it) or hang (because it is no longer drawing anything visible).  If this is the case, changing the exit condition so it's based on the value of x1 should sort things out.

another possibility is the assignment of values to y1.   Check to make sure that indeed y1 is assigned the value you want, and that this value persists across trials.  The simplest way to test this out is to set the value of y1 immediately before the loop (although this is not good programming practice, it's a clear way to be sure that y1 has the desired value).   

In cases like these I find it's useful to employ the debug.print function as part of the inline code - for example here displaying the value of x1,y1 to the output window while the experiment is running.

hope this helps!
david
________________________________________
From: e-prime at googlegroups.com [e-prime at googlegroups.com] on behalf of BeckyL [lundwall.becky at gmail.com]
Sent: 27 January 2012 18:59
To: E-Prime
Subject: creating an oscillating bar using an inline element

I am trying to use the pstnet a modification of the sample "Simple
Animation/Apparent Motion Example" and to create a new task. I have EP
2 and am using Windows XP. I have tried using the E-prime Reference
Guide and Online E-Basic help but they are not specific enough to
solve the problem below with my code. I am having trouble getting the
line to move horizontally instead of diagonally up and right
(eventually I want it to oscillate in place instead of move off the
screen, but that is another step).

ORIGINAL CODE

'Loop continuously until the lines are off screen.
Do Until y1 = 30

   'Increment and decrement coordinates.
   x1 = x1 + 1

   y1 = y1 - 1

   'Wait until the screen refreshes to avoid partial displays.
   Display.WaitForVerticalBlank

   'Clear the screen and draw the new lines.
   cnvs.Clear

   cnvs.Line x1, y1, x1, y1 + lineLen

Loop


Logically, it seems that the next step would be to specify that x1 =
x1 + 1 but y1 remain at 50 (or that y1 = y1). This works for the first
trial but crashes for the second trial.

Could someone please give more guidance on specifying coordinates for
movement? Thank you!

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