Using a hillshade and the height map, generates a semi-transparent hillshade to layer onto an existing map.

generate_altitude_overlay(
  hillshade,
  heightmap,
  start_transition,
  end_transition = NULL,
  lower = TRUE
)

Arguments

hillshade

The hillshade to transition into.

heightmap

A two-dimensional matrix, where each entry in the matrix is the elevation at that point. All grid points are assumed to be evenly spaced.

start_transition

Elevation above which `hillshade` is completely transparent.

end_transition

Default `NULL`. Elevation below which `hillshade` is completely opaque. By default, this is equal to `start_transition`.

lower

Default `TRUE`. This makes `hillshade` completely opaque below `start_transition`. If `FALSE`, the direction will be reversed.

Value

4-layer RGB array representing the semi-transparent hillshade.

Examples

#Create a bathymetric hillshade # \donttest{ water_palette = colorRampPalette(c("darkblue", "dodgerblue", "lightblue"))(200) bathy_hs = height_shade(montereybay, texture = water_palette) plot_map(bathy_hs)
#Set everything below 0m to water palette montereybay %>% sphere_shade(zscale=10) %>% add_overlay(generate_altitude_overlay(bathy_hs, montereybay, 0, 0)) %>% add_shadow(ray_shade(montereybay,zscale=50),0.3) %>% plot_map()
#Add snow peaks by setting `lower = FALSE` snow_palette = "white" snow_hs = height_shade(montereybay, texture = snow_palette) #Set the snow transition region from 500m to 1200m montereybay %>% sphere_shade(zscale=10, texture = "desert") %>% add_overlay(generate_altitude_overlay(bathy_hs, montereybay, 0, 0)) %>% add_overlay(generate_altitude_overlay(snow_hs, montereybay, 500, 1200, lower=FALSE)) %>% add_shadow(ambient_shade(montereybay,zscale=50,maxsearch=100),0) %>% plot_map()
# }