A checkerboard pattern. Includes options for flicker and phase drift. For checkerboard retinotopy using isolated bars see element type checkerboardRetinotopy.

No—runs until any condition you set in property end.

size

Default: square with sides 10 deg

A number that is side length for a square checkerboard, or a vector [width height] for a rectangle (deg).

numChecks

Default: 20 square checks across checkerboard width

Number of checks across the width of the checkerboard. Number of checks across its height is then automatic to give square checks.

Or a vector [n_w n_h] setting number of checks across width and height independently. You can use this if you want non-square checks.

orientation

Default: horizontal and vertical

Orientation angle of the checkerboard, + = clockwise (deg). 0 = horizontal and vertical rows/columns of checks. This sets rotation of the checkerboard within its rectangular display area. If you want rotation of the whole display, use property rotation.

phase

Default: first check right and below center is light

0/1 setting the initial pattern: 0 = first check right and below display center is dark, 1 = light. Currently the checkerboard is always centered at element position, with the corners of four checks at that point. Element position can be set in property position.

meanIntensity
amplitude
contrast

Defaults: meanIntensity = 0.5, amplitude = 0.5

meanIntensity is a number between 0–1 (black–maximum) setting the mean intensity of dark and light checks.

Also set one of amplitude OR contrast:

amplitude is intensity of light checks − intensity of dark checks.

contrast is Michelson contrast, amplitude / mean intensity. If you set contrast, mean intensity must be > 0.

Intensity always clips at 0 and 1. It's possible to set a combination of these properties that causes the checkerboard to clip in this way. See record properties maxAmplitude and maxContrast below.

color

Default: white <cd>[1 1 1]<cd>

A 1×3 RGB vector with numbers between 0–1. This defines the color at intensity = 1. Color at intensity = 0 is <cd>[0 0 0]<cd>. Color at intensities between 0–1 is linearly interpolated between the two. Note intensity, as defined by amplitude/contrast + meanIntensity above, always clips at 0 and 1, so color clips at <cd>[0 0 0]<cd> and color.

flickerFrequency
temporalFrequency
temporalFrequencyBalanced

Defaults: no flicker or phase drift

You can set one of flickerFrequency, temporalFrequency, OR temporalFrequencyBalanced:

flickerFrequency is frequency of switching between dark–light checks (cycles/sec). 0 = no flicker.

temporalFrequency is continuous phase drift rate. This is a 1×2 vector [v_x v_ y] specifying a rate for either horizontal or vertical drift (cycles/sec). You can only do horizontal OR vertical, so leave the other number at 0. The number you set can be positive or negative to specify direction (+ = right/down, − = left/up, at orientation above = 0).

temporalFrequencyBalanced is similar except alternating rows (horizontal) or columns (vertical) drift in opposite directions, creating an internally counterbalanced phase drift. Here +/− effectively determines which rows/columns move in which direction.

position
nn_eyes
rotation
colorMask
alpha
intensity
contrastMult
drawCodeVars

maxAmplitude
maxContrast

Maximum amplitude and contrast where intensity would clip at 0 or 1, whichever is reached first, given the set mean intensity.