A circular checkerboard pattern. Includes options for scaling of radial check sizes (e.g. for cortical scaling), flicker, and angular phase drift. You can also show solid concentric rings if you set number of angular checks = 1. This element type also includes two animation options commonly used in retinotopy tasks:

(1) wedges: show a sequence of isolated wedges by stepping an aperture angularly around the dartboard
(2) rings: show a sequence of isolated rings by stepping an aperture radially through the dartboard

For just a static dartboard or with flicker only, see element type dartboard. See also checkerboardRetinotopy.

"Ends on its own" means ends automatically at that point. If an element can end on its own, you don't need to set end conditions for it in property end (unless you want it to maybe end earlier).

diameter          
centerDiameter

Default: diameter = 10 deg
Default: centerDiameter = 0.2 deg

diameter is diameter of the dartboard (deg).

centerDiameter is diameter of the center area, which is transparent (deg).

numAngularChecks
numRadialChecks

Default: numAngularChecks = 20
Default: numRadialChecks = 8

numAngularChecks is number of segments (light or dark) around the dartboard at any radius.

numRadialChecks is number of segments in any radial line, from edge of the transparent center area to outer edge of the dartboard.

e.g. numAngularChecks = 4, numRadialChecks = 1 → a dartboard consisting of four segments in quadrants.

radialScale

Default: equal radial check sizes

You can use this property to apply cortical (or other) scale factors to check sizes in the radial direction. This is a vector of numbers > 0 that are radial check sizes, from innermost to outermost. Number of sizes must = numRadialChecks above. The absolute magnitudes of the sizes don't matter, only their magnitudes relative to each other. Actual radial sizes are automatically scaled to fit numRadialChecks into the radius from edge of the transparent center area to outer edge of the dartboard.

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 dartboard is always centered at element position, with a boundary between checks along the right horizontal bisector. However, you can change element position in property position, and orientation about its center in property rotation.

meanIntensity
amplitude
contrast

Defaults: mean intensity = 0.5, amplitude = 0.5 → black & maximum intensity

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 max intensity − mean intensity.

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

Intensity always clips at 0 and 1. It's possible to set a combination of these properties that causes the dartboard 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
angularTemporalFrequency
angularTemporalFrequencyBalanced

Default: no flicker or phase drift

You can set one of flickerFrequency, angularTemporalFrequency, OR angularTemporalFrequencyBalanced:

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

angularTemporalFrequency is continuous phase drift rate in the angular dimension, i.e. rotation rate. This can be positive or negative to specify direction (+ = clockwise, − = counterclockwise, check cycles/sec). 0 = no phase drift.

angularTemporalFrequencyBalanced is similar except alternating rings of checks rotate in opposite directions, creating an internally counterbalanced phase drift. Here +/− effectively determines which rings move in which direction. (Note these are just rings on the dartboard, one check wide and evenly spaced. These are different from "ring apertures" below, which can have any width and overlap.)

You can combine using these properties with wedge/ring apertures below.

wedgeVelocity
ringVelocity

Defaults: no wedges or rings—show whole dartboard

You can set one of wedgeVelocity OR ringVelocity:

wedgeVelocity lets you show a sequence of isolated wedges by stepping an aperture angularly around the dartboard. Velocity is rate and direction (angular checks/sec, + = clockwise, − = counterclockwise).

ringVelocity is similar but for isolated rings stepping radially through the dartboard. Velocity is rate and direction (radial checks/sec, + = outward, − = inward).

In both cases aperture size is set in apertureSize below (checks), and the aperture moves in steps settable in apertureStepSize below (checks/step). Velocity (checks/sec) ÷ apertureStepSize (checks/step) gives steps/sec, i.e. how often the aperture steps. (Note for rings, if you set radialScale above to unequal check sizes, currently the aperture changes speed, size, and step size in terms of distance on screen as it moves through radii since those are all set in terms of number of checks.)

apertureSize
apertureStepSize
aperturePhase

Default: apertureSize = 2 checks
Default: apertureStepSize = 1 check/step
Default: aperturePhase = 0 → see below

If you set wedgeVelocity or ringVelocity:

apertureSize is wedge or ring width (checks).

apertureStepSize is how far the wedge or ring moves at each step (checks).

aperturePhase is for wedges only. It sets the initial wedge shown. It is a number of angular checks clockwise. What zero means depends on wedgeVelocity: 0 = first wedge below the right horizontal bisector if wedgeVelocity > 0, or first wedge above if wedgeVelocity < 0. You can also change orientation of the whole display about its center in property rotation.

For rings, initial ring is always the innermost ring if ringVelocity > 0, or the outermost ring if ringVelocity < 0.

Note these numbers can be fractional, not just integer.

maxNumLoops

Default: show one pass through the dartboard

If you set wedgeVelocity or ringVelocity, maxNumLoops is a number > 0 that is number of passes through the dartboard to show, after which the object ends. Note this number can be fractional, not just integer. <cd>inf<cd> = repeat until a condition you set in property end.

position
nn_eyes
rotation
colorMask
alpha
intensity
contrastMult
drawCodeVars

maxAmplitude
maxContrast

Values for input properties amplitude and contrast that would cause intensity to clip at 0 or 1 given the current value of meanIntensity.