Pattern Center

Center allows you to specify the location of the pattern’s center relative to the region in which it is embedded. The center coordinates can be specified in degrees of visual angle, pixels, or centimeters.

By default, the coordinate frame is centred in the middle of the region.

Adjusting the center of a pattern can be helpful can be useful when fine-tuning the disparity of two grating patterns which will be viewed binocularly. The grating's center can be specified as relative to the center of the testing display, or relative to the center of the region holding the grating.

If you are planning on moving the region, and you want the grating to stay stuck to the screen (giving the impression that the region is a window moving over a fixed grating), then turn off the From center of region checkbox in the center parameters. Otherwise, leave this checkbox turned on. Now if you drag the region, the grating pattern will remain unchanged within the region.

LabMaestro also offers the flexibility of specifying the center in rectangular or polar coordinates.

Geometric polar coordinates have their 0-degree origin towards the right, with increasing angles rotating counter-clockwise. Geographic polar coordinates have 0 degrees towards the top of the display, with increasing angles rotating clockwise.

The polar coordinate systems are convenient if you conceptualize your stimulus location in terms of visual eccentricity and meridian.

Changing the coordinate space buttons or the linear units popup will cause LabMaestro to automatically convert the existing coordinates to the new space and units.