# Changing position of aperture in DriftDemo2.m **URL:** \ **Category:** Uncategorized\ **Created:** [November 7, 2011, 6:45pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471 "2011-11-07T18:45:01Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![pikki.hogan](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@pikki.hogan](https://psychtoolbox.discourse.group/u/pikki.hogan)\ **Post date:** [November 7, 2011, 6:45pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/1 "2011-11-07T18:45:01Z")
Hello, I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? Thank you very much. Best, Pik Ki ---
**Author:** ![xrli2002](https://avatars.discourse-cdn.com/v4/letter/x/48db29/32.png) [@xrli2002](https://psychtoolbox.discourse.group/u/xrli2002)\ **Post date:** [November 7, 2011, 9:39pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/2 "2011-11-07T21:39:17Z")
It should work. Most likely, you messed up the numbers in the rect. They are [left top right bottom]. Topleft cornner is [0 0]. Xiangrui > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> > \> Hello, > \> > \> I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? > \> > \> Thank you very much. > \> > \> Best, > \> Pik Ki > \> ---
**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\ **Post date:** [November 8, 2011, 12:24am UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/3 "2011-11-08T00:24:34Z")
Indeed. E.g., dstRect = CenterRectOnPoint(dstRect, 200, 300); insted of CenterRect() line would center the grating to pixel position (x,y) = (200, 300). "help PsychRects" -mario > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "xrli2002" \ wrote: > \> > \> It should work. Most likely, you messed up the numbers in the rect. They are [left top right bottom]. Topleft cornner is [0 0]. > \> > \> Xiangrui > \> > \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> \> > \> \> Hello, > \> \> > \> \> I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? > \> \> > \> \> Thank you very much. > \> \> > \> \> Best, > \> \> Pik Ki > \> \> > \> ---
**Author:** ![pikki.hogan](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@pikki.hogan](https://psychtoolbox.discourse.group/u/pikki.hogan)\ **Post date:** [November 7, 2011, 11:38pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/4 "2011-11-07T23:38:43Z")
Hi Xiangrui, Thanks for your reply. That's what I thought as well but I'm pretty sure the coordinates I entered are valid... Best, Pik Ki > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "xrli2002" \ wrote: > \> > \> It should work. Most likely, you messed up the numbers in the rect. They are [left top right bottom]. Topleft cornner is [0 0]. > \> > \> Xiangrui > \> > \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> \> > \> \> Hello, > \> \> > \> \> I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? > \> \> > \> \> Thank you very much. > \> \> > \> \> Best, > \> \> Pik Ki > \> \> > \> ---
**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\ **Post date:** [November 8, 2011, 1:07pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/5 "2011-11-08T13:07:45Z")
Nope, Xiangrui is right, it will work if you don't make a mistake. I assume your psychtoolbox is not outdated by years or something else is seriously broken on your computer. -mario > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> > \> Hi Xiangrui, > \> > \> Thanks for your reply. That's what I thought as well but I'm pretty sure the coordinates I entered are valid... > \> > \> Best, > \> Pik Ki > \> > \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "xrli2002" \ wrote: > \> \> > \> \> It should work. Most likely, you messed up the numbers in the rect. They are [left top right bottom]. Topleft cornner is [0 0]. > \> \> > \> \> Xiangrui > \> \> > \> \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> \> \> > \> \> \> Hello, > \> \> \> > \> \> \> I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? > \> \> \> > \> \> \> Thank you very much. > \> \> \> > \> \> \> Best, > \> \> \> Pik Ki > \> \> \> > \> \> > \> ---
**Author:** ![pikki.hogan](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@pikki.hogan](https://psychtoolbox.discourse.group/u/pikki.hogan)\ **Post date:** [November 8, 2011, 12:05pm UTC](https://psychtoolbox.discourse.group/t/changing-position-of-aperture-in-driftdemo2-m/471/6 "2011-11-08T12:05:27Z")
Thanks Mario, that worked! :D > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> > \> Hi Xiangrui, > \> > \> Thanks for your reply. That's what I thought as well but I'm pretty sure the coordinates I entered are valid... > \> > \> Best, > \> Pik Ki > \> > \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "xrli2002" \ wrote: > \> \> > \> \> It should work. Most likely, you messed up the numbers in the rect. They are [left top right bottom]. Topleft cornner is [0 0]. > \> \> > \> \> Xiangrui > \> \> > \> \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Pik Ki" \ wrote: > \> \> \> > \> \> \> Hello, > \> \> \> > \> \> \> I'm trying to program a grating oscillating within a circular aperture and I've found the DriftDemo2 in PsychDemos particularly useful. However, I noticed that the dstRect is put in the centre of the screen using CenterRect. I tried changing the position of the aperture by redefining dstRect (i.e. giving new coordinates) but then the screen just turned blank. Would anyone give me some advice what I should have done if I want the drifting grating to appear not the centre, but elsewhere on the screen? > \> \> \> > \> \> \> Thank you very much. > \> \> \> > \> \> \> Best, > \> \> \> Pik Ki > \> \> \> > \> \> > \>