A checkerboard pattern, including options for flicker and internal phase drift.

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. This sets rotation of the checkerboard within its rectangular display area. For 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. Note 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 pixel intensity of dark and light checks.

Also set one of:

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

OR

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

It's possible to set a combination of these properties that causes the checkerboard to clip at intensity 0 or 1. See record properties maxAmplitude and maxContrast below.

color

Default: white

A 1×3 RGB vector with numbers between 0–1. This defines the color at pixel intensity = 1. Color at intensity = 0 is <cd>[0 0 0]<cd>. Color at all other intensities is linearly interpolated between the two.

flickerFrequency
flickerVelocity

Defaults: no flicker / internal phase drift

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

flickerVelocity lets you set a more continuous form of "flicker" where alternating rows or columns of the checkerboard drift in opposite directions at a specified speed, creating an internal phase drift. To do this, set flickerVelocity to a 1×2 vector [v_x v_ y] specifying a velocity for either horizontal or vertical internal drift (cycles/sec). +/− effectively determines which rows/columns go in which direction. You can only do horizontal or vertical, not both, so leave the other number at 0.

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.