#30DayMapChallenge 2022 - Day 19 - Globe

day_19_globe.R

# Animate an expanding buffer around land, with a "globe" view of the Pacific

library(glue)
library(stringr)
library(dplyr)
library(purrr)
library(sf)
library(rnaturalearth)
library(ggplot2)
library(av)

CRS_GLOBE <- "+proj=ortho +lat_0=-10 +lon_0=-160 +x_0=0 +y=0=0 +a=6371000 +b=6371000 +units=m +no_defs"
COLOUR_BG <- "grey10"
COLOUR_OCEAN <- "light blue"
COLOUR_LAND <- "dark green"

ocean <- 
  st_point(x = c(0, 0)) |> 
  st_buffer(dist = 6371000) |> 
  st_sfc(crs = CRS_GLOBE)

plot_the_frame <- 
  function(land_buffer) {
    land_buffered <- 
      ne_countries(scale = "large", returnclass = "sf") |> 
      st_buffer(land_buffer) |> 
      st_intersection(ocean |> st_transform(crs = 4326L)) |> 
      st_transform(crs = CRS_GLOBE)
    
    gg_frame <- 
      ggplot() +
      geom_sf(data = ocean, fill = COLOUR_OCEAN, colour = NA) +
      geom_sf(data = land_buffered, fill = COLOUR_LAND, colour = NA) +
      theme_void() +
      theme(plot.background = element_rect(fill = COLOUR_BG, colour = COLOUR_BG),
            panel.background = element_rect(fill = COLOUR_BG, colour = COLOUR_BG))
    
    ggsave(plot = gg_frame,
           filename = glue("frame_{str_pad(land_buffer, 6, pad = '0')}.png"),
           path = "Day_19_Globe/frame/",
           height = 8, width = 8)
  }

(0:400 * 1000) |> 
  walk(plot_the_frame)

av_encode_video(list.files(path = "Day_19_Globe/frame", pattern = "png", full.names = TRUE),
                framerate = 30,
                output = "Day_19_Globe/Day_19_globe.mp4")