3D polygon layer

tmap.mapgl also features a new layer type, tm_polygons_3d, which is only available for the "mapbox" and "maplibre" modes.

This map layer is the same as tm_polygons, with one addition: polygons can be extruded into 3D shapes. The visual variable to control this is called height.

Example: buildings heights

tmap_mode("maplibre")

# get vector buildings
library(osmdata)
buildings <- opq(bbox = "Marina Bay, Singapore") |>
    add_osm_feature(key = "building") |>
    osmdata_sf()

library(dplyr, warn.conflicts = FALSE)
# only keep polygons
buildings_poly <- buildings$osm_polygons |>
  # convert height and levels from string to numeric
  mutate(levels = as.numeric(`building:levels`),
         height = as.numeric(height)) |>
  # assume 2 levels if NA
  mutate(levels = if_else(is.na(levels), 2, levels),
         # assume height of 3 m per level if no height
         height = if_else(is.na(height), levels * 3, height))

For the time being, we need to compute the maximum building height, because tm_scale_asis doesn’t support units yet.

# maximum building height
mx = max(buildings_poly$height)

# plot
tm_shape(buildings_poly) +
    tm_polygons_3d(height = "height", options = opt_tm_polygons_3d(height.max = mx)) + 
    tm_maplibre(pitch = 60)

Example: population density data (Netherlands)

NLD_dist$pop_dens = NLD_dist$population / NLD_dist$area

tm_shape(NLD_dist) +
  tm_polygons_3d(height = "pop_dens",
    fill = "edu_appl_sci",
    fill.scale = tm_scale_intervals(style = "kmeans", values = "-pu_gn"),
    fill.legend = tm_legend("University degree")) +
tm_maplibre(pitch = 45) +
tm_crs(3857)
#> [plot mode] map layer `tm_polygons_3d` not available for mode "plot". This map
#> layer is only available for modes "mapbox" and "maplibre"
#> [nothing to show] no data layers defined after `tm_shape()`

The last code line is to enable the mercator projection. The default projection, “globe” is similar at this zoom level, but triggers some artefacts around the polygon borders.