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hillshader

The hillshader package is a wrapper around the rayshader and raster packages to create hillshade relief maps using ray-tracing, and write them to (spatial) files.

Installation

The stable version of hillshader can be installed from CRAN:

install.packages("hillshader")

Alternatively, if you feel brave, you can install the development version of hillshader with the remotes package:

remotes::install_github("pierreroudier/hillshader")

First steps

Below is a quick tutorial of the hillshader capabilities:

The hillshader function

The hillshader function is the main function of that package, and allows to create a hillshade map as a RasterLayer:

library(raster)
#> Loading required package: sp
library(rayshader)

library(hillshader)

Note that the hillshader package includes the maungawhau and maungawhau_hr datasets. These are geo-referenced, raster datasets. maungawhau corresponds to the well-known volcano dataset. It is a 87 × 61 elevation matrix for Maungawhau, one of the circa 80 volcanoes in the Auckland volcano filed, in Aotearoa/New Zealand. The maungawhau_hr dataset is a “high-resolution” version of that dataset, and is a 1 m resolution, 860 × 600 elevation matrix derived from a LiDAR dataset recorded by NZ Aerial Mapping & Aerial Surveying Limited for Auckland Council, and distributed by Land Information New Zealand.

layout(matrix(c(1,2), nrow = 1, ncol = 2))
image(maungawhau, asp = 1, main = "Maungawhau", col = terrain.colors(100))
image(maungawhau_hr, asp = 1, main = "Maungawhau (high-resolution)", col = terrain.colors(100))

The hillshader function can be simply called on a elevation raster to generate a hillshade RasterLayer. By default, the shader used is rayshader::ray_shade, with its default values.

hs <- hillshader(maungawhau_hr)
plot_map(hs)

Add more shaders!

The hillshader function accept a shader option, with is a list of the successive shader functions to apply to create the hillshade layer. The accepted values must be rayshader shader functions (ray_shade, ambient_shade, lamb_shade), and the order is important.

hs <- hillshader(
  elevation = maungawhau_hr, 
  shader = c("ray_shade", "ambient_shade")
)

plot_map(hs)

Changing sun position

The hillshader function uses the rayshader options defaults, but other values can be specify and passed as arguments:

hs <- hillshader(
  elevation = maungawhau_hr, 
  shader = c("ray_shade", "ambient_shade"),
  sunangle = 180,
  sunaltitude = 25
)

plot_map(hs)

How does it compare to your usual hillshade method?

library(raster)

slope <- terrain(maungawhau_hr, out = "slope")
aspect <- terrain(maungawhau_hr, out = "aspect")
hs_raster <- hillShade(
  slope, 
  aspect, 
  angle = 40, 
  direction = 325
)

hs_hillshader <- hillshader(
  maungawhau_hr, 
  c("ray_shade", "ambient_shade"),
  sunangle = 325,
  sunaltitude = 40
)

layout(matrix(c(1,2), nrow = 1, ncol = 2))
image(hs_raster, asp = 1, main = "Classic hillshade", col = grey.colors(100))
image(hs_hillshader, asp = 1, main = "Ray-traced hillshade", col = grey.colors(100))

Saving to file

If a filename is passed to hillshader, then the resulting hillshade layer is saved to file. This is a wrapper around raster::writeRaster, and options specific to the latter function can be used.

hillshader(
  elevation = maungawhau_hr, 
  shader = c("ray_shade", "ambient_shade"),
  sunangle = 180,
  sunaltitude = 25,
  filename = "hillshade.tif"
)

Advanced use in the rayshader pipelines

The hillshader package provides three functions that can be used within the rayshader pipelines:

• add_shadow_2d: a function that multiplies a shadow map by another shadow map, a corrected 2D version of rayshader::add_shadow,
• matrix_to_raster: a function that converts a matrix (typically used by the rayshader functions) back to a RasterLayer, for input into a GIS workflow,
• write_raster: a function that a hillshade matrix to a raster file format.

library(rayshader)
library(hillshader)

# Create elevation matrix
el_mat <- raster_to_matrix(maungawhau_hr)

el_mat %>%
  # Create hillshade layer using 
  # ray-tracing
  ray_shade %>%
  # Add ambient shading
  add_shadow_2d(
    ambient_shade(
      heightmap = el_mat
    )
  ) %>% 
  # Write to GIS file
  write_raster(
    elevation = maungawhau_hr,
    filename = "hillshade.tif"
  )

Code of Conduct

Please note that the hillshader project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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