R: Generate Altitude Overlay

generate_altitude_overlay {rayshader} | R Documentation

## Generate Altitude Overlay

### Description

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

### Usage

    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
    #Only run these examples if the `magick` package is installed.
    if ("magick" %in% rownames(utils::installed.packages())) {

    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()

    }

[Package rayshader version 0.24.10 Index]