Tools for Multiple Object Tracking experiments • motrack

Multiple Object Tracking is a popular experimental paradigm used in visual attention research. Your goal is to remember several objects and keep track of the them while they move (demo).

This package allows researcher to generate object trajectories, visualize them and export them for experiments. The trajectory and position data are in tibble format for easy further manipulation.

Installation

The package is in active development. You can install the current version from GitHub with following code:

# Install devtools package if necessary
if(!"devtools" %in% rownames(installed.packages())) install.packages("devtools")

# Install the stable verion from GitHub
devtools::install_github("visionlabels/motrack")

Example

Let us create a trajectory or two:

library(motrack) #load the package

# we want objects starting 
# more further from the arena border and further from each other
sett_generate <-
  new_settings(xlim = c(-7, 7), ylim = c(-7, 7), min_distance = 2,
               arena_shape = "circle")
# they can move in a circular arena, bounce off borders and other objects
sett_move <-
  new_settings(speed = 5, xlim = c(-9, 9), ylim = c(-9, 9),
               bounce_off_square = F,
               bounce_off_circle = T, circle_bounce_jitter = pi / 6)
# here you can separately adjust settings for visualization
sett_show <-
  new_settings(show_labels = T)

# set seed for replicability
set.seed(1001)

position <- generate_positions_random(8, sett_generate)

# our starting positions
plot_position(position, sett_move)

# Make objects move for 8 seconds (0 to 8), adjust direction every 100 ms
timescale <- seq(0, 8, by = 0.1)

# Objects only bounce
trajectory_d <- 
  make_random_trajectory(position, timescale, sett_move, 
    step_direct)

# Object change direction randomly every 0.5-1.5 seconds
trajectory_z <- 
  make_random_trajectory(position, timescale, sett_move, 
    step_zigzag, ttt = c(.5, 1.5), syncstart = F)

# Object change direction smoothly
trajectory_v <- 
  make_random_trajectory(position, timescale, sett_move, 
    step_vonmises, kappa = 10)

plot_trajectory(trajectory_d, sett_show)
plot_trajectory(trajectory_z, sett_show)
plot_trajectory(trajectory_v, sett_show)

# It is possible to implement complex motion patterns:
# Object move for 0.5-1.5 seconds or wait for 0.2-0.5 seconds. 
# After movement/waiting, it waits with probability 0.1, 
# otherwise it changes direction randomly
trajectory_wm <- 
  make_random_trajectory(
    position, timescale, sett_move, 
    step_waitandmove, move_time = c(.5, 1.5), 
    wait_time = c(.2,.5), wait_prob = 0.1, syncstart = F)

# It is possible to vary speed during the trial based on the custom function
f1 <- function(time, moment) {
  5 + cos(time + moment$object) # different offset for each object
}
sett_move$speed <- c(f1)

trajectory_s <- 
  make_random_trajectory(
    position, timescale, sett_move, step_direct)

If you have ffmpeg installed, you can use animation package to render videos.

animation::ani.options(ffmpeg = "/usr/bin/ffmpeg")   # update to your path

render_trajectory_video("trajectory_d.mp4", trajectory_d, 
  new_settings(show_labels = T), targets = 1:4
)
render_trajectory_video("trajectory_z.mp4", trajectory_z, 
  new_settings(show_labels = T), targets = 1:4
)
render_trajectory_video("trajectory_v.mp4", trajectory_v, 
  new_settings(show_labels = T), targets = 1:4
)

# variable speed example
render_trajectory_video("trajectory_s.mp4", trajectory_s, 
  new_settings(show_labels = T), targets = 1:4
)

motrack - tools for Multiple Object Tracking

Installation

Example