Moving Dots

Description

A moving dot field stimulus

Signature

stimulus/moving_dots

Required Parameters

field_radius

Field radius (degrees)

dot_density

Number of dots per square degree

dot_size

Dot diameter (degrees)

speed

Dot speed (degrees per second)

Optional Parameters

field_center_x

Default

0.0

Field horizontal center position (degrees)

field_center_y

Default

0.0

Field vertical center position (degrees)

color

Default

1.0,1.0,1.0

Dot color, expressed as a comma-separated list of red, green, and blue components. Each component may be described by any valid expression, but the expression must result in a value between 0 and 1 (inclusive).

alpha_multiplier

Default

1.0

Controls the transparency of the dots. 1.0 is fully opaque, while 0.0 is fully tranparent.

direction

Default

0.0

Direction of movement for coherent dots (degrees)

coherence

Default

1.0

Fraction of dots that move in the specified direction. Non-coherent dots receive random directions.

lifetime

Default

0.0

Dot lifetime (seconds). When a dot reaches the end of its lifetime, it is removed and replaced by a new dot in a random location.

announce_dots

Default

NO

If YES, stimulus announcements (i.e. #stimDisplayUpdate events) will include dot positions.

Position data is encoded as a binary array of single-precision floating point values (in platform byte order), with each consecutive pair of values representing the (x,y) coordinates of a dot. The coordinates are scaled to lie in the range [-1,1] and rotated so that the direction of coherent motion is zero degrees.

rand_seed

Seed value for the random number generator. If omitted, the current system time in nanoseconds is used.

deferred

Options
no
yes
explicit
Default

no

Controls when the stimulus is loaded. If no, the stimulus is loaded at experiment load time. If yes, the stimulus is loaded the first time it is queued. If explicit, the stimulus must be loaded explictly with Load Stimulus.

autoplay

Default

NO

If YES, the stimulus will start playing automatically (as if by an implicit Play Dynamic Stimulus action) after it has been queued and Update Stimulus Display has been invoked. It will also stop playing automatically (as if by an implicit Stop Dynamic Stimulus action) after it has been dequeued and Update Stimulus Display is invoked.