Lissajous.R

# See gif at https://twitter.com/_Axeman_/status/1041286690357354496
library(tidyverse)
library(gganimate)

# This function does the basic clculations for a data.frame of circular coordinates
find_circular_coords <- function(speed, row, column) {
  steps <- 300
  data_frame(
    time = 1:steps,
    angle = rep(seq(0, 2*pi, length.out = steps / speed), times = speed),
    x = cos(angle) * 0.6 + row * 2,
    y = sin(angle) * 0.6 + column * 2,
  )
}

# To calculate average colors trhough lab space
average_colors <- function(col1, col2) {
  lab1 <- convertColor(t(col2rgb(col1)/256), 'sRGB', 'Lab')
  lab2 <- convertColor(t(col2rgb(col2)/256), 'sRGB', 'Lab')
  lab <- (lab1 + lab2) / 2
  col <- as.list(convertColor(lab, 'Lab' , 'sRGB'))
  do.call(rgb, col)
}

# First find the outside reference cicles, with different speeds
reference_circles <- bind_rows(
  'r1' = find_circular_coords(1, 1, 2),
  'r2' = find_circular_coords(2, 1, 3),
  'r3' = find_circular_coords(3, 1, 4),
  'r4' = find_circular_coords(4, 1, 5),
  'r5' = find_circular_coords(5, 1, 6),
  'c1' = find_circular_coords(1, 2, 1),
  'c2' = find_circular_coords(2, 3, 1),
  'c3' = find_circular_coords(3, 4, 1),
  'c4' = find_circular_coords(4, 5, 1),
  'c5' = find_circular_coords(5, 6, 1),
  .id = 'circle'
)
# add colors
circle_info <- data_frame(
  circle = c('r1', 'r2', 'r3', 'r4', 'r5', 'c1', 'c2', 'c3', 'c4', 'c5'),
  color = rep(c('yellow', 'green', 'blue', 'purple', 'red'), 2)
)
reference_circles <- left_join(reference_circles, circle_info, by = "circle")

# Join the different combinations of outer circles together, to create the inner circles
inner_circles <- expand.grid(
  row    = paste0('r', 1:5), 
  column = paste0('c', 1:5),
  stringsAsFactors = FALSE
) %>%
  as_tibble() %>% 
  right_join(select(reference_circles, circle, time, y, color_x = color), by = c('row' = 'circle')) %>% 
  right_join(select(reference_circles, circle, time, x, color_y = color), by = c('column' = 'circle', 'time')) %>% 
  mutate(
    circle = paste0(row, column),
    color = map2_chr(color_x, color_y, average_colors)
  )
# Make one big data.frame
combined <- bind_rows(reference_circles, inner_circles)

# Calculate the horizontal and vertical lines that connect the coordinates
hor_segments <- inner_circles %>% 
  filter(column == 'c5') %>% 
  select(row, column, x_end = x, y_end = y, time) %>% 
  left_join(
    select(reference_circles, circle, x_start = x, y_start = y, time), 
    by = c('row' = 'circle', 'time')
  ) %>% 
  rename(circle = row)

ver_segments <- inner_circles %>% 
  filter(row == 'r5') %>% 
  select(row, column, x_end = x, y_end = y, time) %>% 
  left_join(
    select(reference_circles, circle, x_start = x, y_start = y, time), 
    by = c('column' = 'circle', 'time')
  ) %>% 
  rename(circle = column)

segments <- bind_rows(hor_segments, ver_segments)

# Plot and animate
p <- ggplot(combined, aes(x, y, group = circle)) + 
  geom_path(aes(color = color), size = 1.5) + 
  geom_segment(
    aes(x = x_start, xend = x_end, y = y_start, yend = y_end),
    data = segments, lty = 2, color = 'grey80'
  ) +
  geom_point(data = reference_circles, fill = 'white', color = 'black', shape = 21, size = 4) + 
  geom_point(data = inner_circles, color = 'black', size = 1.5) + 
  coord_equal() + 
  scale_y_reverse() +
  scale_color_identity() +
  transition_reveal(circle, time) +
  ease_aes(default = 'linear') +
  theme_void() +
  theme(legend.position = 'none', plot.background = element_rect(fill = 'black'))

# Save the animation
anim_save(
  'test.gif', 
  animate(p, 300, 30)
)