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Best way to draw full-screen mask over stimuli already shown in aperture?

Hi,

I have full-screen motion stimuli (gratings) drawn with visual.ElementArrayStim and use visual.Aperture to mask the outer edge shape of the stimulus display. That is all working well!

But I’m stuck on the best way to draw one final mask - I’d like to show only a rectangular area of the whole screen at a time (and the area shown will change every 2 sec). Changing visual.Aperture isn’t an option because I need to show other elements on the screen like a fixation cross that are outside the stimulus aperture.

Is there a way to do something like overlay a mask of background color over the whole screen with a rectangular transparent region? And easily change the orientation and screen position of the transparent rectangle every few secs?

Any suggestions welcome - thanks!

Isn’t this just a matter of drawing order? i.e. draw with your aperture on, then switch it off and then draw the fixation point wherever you want it. Or alter the shape of the aperture and draw again - I’m not really sure what you want.