Generate Polygon Overlay

Transforms an input sf object into an image overlay for the current height map.

generate_polygon_overlay(
  geometry,
  extent,
  heightmap = NULL,
  width = NA,
  height = NA,
  resolution_multiply = 1,
  offset = c(0, 0),
  data_column_fill = NULL,
  linecolor = "black",
  palette = "white",
  linewidth = 1
)

Arguments

geometry

An sf object with POLYGON geometry.

extent

Either an object representing the spatial extent of the scene (either from the raster, terra, sf, or sp packages), a length-4 numeric vector specifying c("xmin", "xmax","ymin","ymax"), or the spatial object (from the previously aforementioned packages) which will be automatically converted to an extent object.

heightmap

Default NULL. The original height map. Pass this in to extract the dimensions of the resulting overlay automatically.

width

Default NA. Width of the resulting overlay. Default the same dimensions as height map.

height

Default NA. Width of the resulting overlay. Default the same dimensions as height map.

resolution_multiply

Default 1. If passing in heightmap instead of width/height, amount to increase the resolution of the overlay, which should make lines/polygons/text finer. Should be combined with add_overlay(rescale_original = TRUE) to ensure those added details are captured in the final map.

offset

Default c(0,0). Horizontal and vertical offset to apply to the polygon, in units of geometry.

data_column_fill

Default NULL. The column to map the polygon fill color to.

linecolor

Default black. Color of the lines.

palette

Default black. Single color, named vector color palette, or palette function. If this is a named vector and data_column_fill is not NULL, it will map the colors in the vector to the names. If data_column_fill is a numeric column, this will give a continuous mapping.

linewidth

Default 1. Line width.

Value

Image overlay representing the input polygon data.

Examples

#Plot the counties around Monterey Bay, CA
if(run_documentation()) {
generate_polygon_overlay(monterey_counties_sf, palette = rainbow, 
                        extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
 plot_map() 
}

if(run_documentation()) {
#These counties include the water, so we'll plot bathymetry data over the polygon
#data to only include parts of the polygon that fall on land.
water_palette = colorRampPalette(c("darkblue", "dodgerblue", "lightblue"))(200)
bathy_hs = height_shade(montereybay, texture = water_palette)

generate_polygon_overlay(monterey_counties_sf, palette = rainbow, 
                        extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
 add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
 plot_map()
}

if(run_documentation()) {
#Add a semi-transparent hillshade and change the palette, and remove the polygon lines
montereybay %>%
 sphere_shade(texture = "bw") %>%
 add_overlay(generate_polygon_overlay(monterey_counties_sf, 
                        palette = terrain.colors, linewidth=NA,
                        extent = attr(montereybay,"extent"), heightmap = montereybay),
                        alphalayer=0.7) %>%
 add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
 add_shadow(ray_shade(montereybay,zscale=50),0) %>%
 plot_map()
}

if(run_documentation()) {
#Map one of the variables in the sf object and use an explicitly defined color palette
county_palette = c("087" = "red",    "053" = "blue",   "081" = "green", 
                  "069" = "yellow", "085" = "orange", "099" = "purple") 
montereybay %>%
 sphere_shade(texture = "bw") %>%
 add_shadow(ray_shade(montereybay,zscale=50),0) %>%
 add_overlay(generate_polygon_overlay(monterey_counties_sf, linecolor="white", linewidth=3,
                        palette = county_palette, data_column_fill = "COUNTYFP",
                        extent = attr(montereybay,"extent"), heightmap = montereybay),
                        alphalayer=0.7) %>%
 add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
 add_shadow(ray_shade(montereybay,zscale=50),0.5) %>%
 plot_map()
}