Create a 3D ggplot with {ggrgl} and colour the extrusion by some variable

gpx3d-extrude-colour.R

# Create a 3D ggplot with {ggrgl} and colour the extrusion by some variable
#
# Motivation via @geoff_tewierik:
#   https://twitter.com/geoff_tewierik/status/1476662279437369346?s=20
# See blog about the {gpx3d} package:
#   https://www.rostrum.blog/2021/12/30/gpx3d/
# See {gpx3d} package source:
#   https://github.com/matt-dray/gpx3d

library(gpx3d)
library(ggplot2)
library(ggrgl)
library(devoutrgl)
library(RColorBrewer)

# Read local GPX file and extract data
route <- extract_gpx3d(
  "~/Downloads/apple_health_export/workout-routes/route_2021-12-25_9.31am.gpx"
)

# I couldn't seem to get the ggrgl::scale_extrude_*() functions to work, so
# this is a low-tech workaround (palette as per https://stackoverflow.com/a/6183993)
my.col <- colorRampPalette(brewer.pal(9, "YlOrRd"))(diff(range(route$ele)))
pal <- my.col[route$ele]

# Create 3D plot
route_plot <- ggplot() +
  geom_path_3d(
    aes(route$lon, route$lat, z = route$ele), 
    extrude = TRUE,
    extrude_face_fill = pal,
    extrude_edge_colour = pal
  ) +
  theme_void()

# Plot to external device
rgldev(fov = 30, view_angle = -30); route_plot; invisible(dev.off())