Given a viewing distance, this function calculates the on-screen diameters of a hypothetical object of defined size approaching at a constant speed. This allows a looming animation with precise parameters to be created.
constant_speed_model(
screen_distance = 20,
frame_rate = 60,
speed = 500,
attacker_diameter = 50,
start_distance = 1000
)Numeric. Distance (cm) from the playback screen to your specimen.
Numeric. Frames per second (Hz) you want the resulting animation to be.
Numeric. Speed (cm/s) of the hypothetical approaching attacker.
Numeric. Diameter (cm) of the hypothetical approaching attacker
Numeric. Starting (cm) distance of the hypothetical approaching attacker
A list object containing the input parameters and the resulting
diameter for each frame in the animation.
Calculates the screen diameters for a modelled object of specified
size approaching at a constant speed, from a specified distance away. The
output list object can be used to create a looming animation in
looming_animation. An object screen diameter is calculated
for each frame from the specified starting distance until the hypothetical
distance between the attacker and target is zero.
Requires the frame rate at which the subsequent animation will be played, and distance from the screen at which the observing specimen will be located. These details are important in experiments where you want to precisely determine at what time, perceived distance, or perceived velocity of an attack an escape response occurs. Note: if the specimen is closer or further away than the specified screen distance, the animation will be perceived as a different distance and a different velocity.
If you need to create a looming animation simply to elicit a response, and
are not concerned with the precise details, see
diameter_model.
Inputs should be in cm, speed in cm/s, and frame rate in Hz (i.e.
frames per second).
loom_model <- constant_speed_model(
screen_distance = 20,
frame_rate = 60,
speed = 500,
attacker_diameter = 50,
start_distance = 1000)