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## Create and Visualize Hillshaded Maps from Elevation Matrices

Uses a combination of raytracing, spherical texture mapping, lambertian reflectance, and ambient occlusion to produce hillshades of elevation matrices. Includes water detection and layering functions, programmable color palette generation, several built-in textures, 2D and 3D plotting options, and the ability to export 3D maps to a 3D printable format.

## Overview

rayshader is an open source package for producing hillshaded maps of elevation matrices with raytracing and spherical texture mapping.

## Installation

# To install the latest version from Github:
# install.packages("devtools")


## Functions

• ray_shade uses user specified light directions to calculate a global shadow map for an elevation matrix. By default, this also scales the light intensity at each point by the dot product of the mean ray direction and the surface normal (also implemented in function lamb_shade, this can be turned off by setting lambert=FALSE.
• sphere_shade maps an RGB texture to a hillshade by spherical mapping. A texture can be generated with the create_texture function, or loaded from an image. sphere_shade also includes 7 built-in palettes: "imhof1","imhof2","imhof3",imhof4","desert","bw","unicorn".
• create_texture programmatically creates texture maps given five colors: a highlight, a shadow, a left fill light, a right fill light, and a center color for flat areas. The user can also optionally specify the colors at the corners, but create_texture will interpolate those if they aren't given.
• ambient_shade creates an ambient occlusion shadow layer, darkening areas that have less scattered light from the atmosphere. This results in valleys being darker than flat areas and ridges.
• lamb_shade uses a single user specified light direction to calculate a local shadow map based on the dot product between the surface normal and the light direction for an elevation matrix.
• add_shadow takes two of the shadow maps above and combines them, scaling the second one (or, if the second is an RGB array, the matrix) as specified by the user.

Rayshader also has two functions to detect and add water to maps:

• detect_water uses a flood-fill algorithm to detect bodies of water of a user-specified minimum area.
• add_water uses the output of detect_water to add a water color to the map. The user can input their own color, or pass the name of one of the pre-defined palettes from sphere_shade to get a matching hue.

And two functions to display and save your maps:

• plot_map Plots the current map. Accepts either a matrix or an array.
• save_png Saves the current map to disk with a user-specified filename.
• plot_3d Creates a 3D map, given a texture and an elevation matrix. You can customize the appearance of the map, as well as add a user-defined water level.
• save_3dprint Writes a stereolithography (STL) file of the current 3D map to create a 3D printable map. The user can specify the physical maximum width of the 3D print when calling the function.

All of these functions are designed to be used with the magrittr pipe %>%.

## Usage

library(rayshader)
library(magrittr)

#Here, I load a map for the River Derwent in Tasmania with the raster package:
localtif = raster::raster("tasmania.tif")

#And convert it to a matrix:
elmat = matrix(raster::extract(localtif,raster::extent(localtif),buffer=1000),
nrow=ncol(localtif),ncol=nrow(localtif))

#We use another one of rayshader's built-in textures:
elmat %>%
plot_map()


#sphere_shade can shift the sun direction:
elmat %>%
sphere_shade(sunangle = 45, texture = "desert") %>%
plot_map()


#detect_water and add_water adds a water layer to the map:
elmat %>%
plot_map()


#And we can add a raytraced layer from that sun direction as well:
elmat %>%
plot_map()


elmat %>%
plot_map()


Rayshader also supports 3D mapping by passing a texture map (either external or one produced by rayshader) into the plot_3d function.

elmat %>%
plot_3d(elmat)


You can also easily add a water layer by setting water = TRUE (and setting waterdepth if the water level is not 0). You can customize the appearance and transparancy of the water layer via arguments to plot_3d. Here's an example using the built-in example bathymetric/topographic data of Monterey Bay, CA montereybay (zscale for a 1-to-1 ratio using montereybay would be 200, but in plot_3d is set to 50 to give a 4x exaggerated height in the z-direction) :

montereybay %>%
plot_3d(montereybay, water=TRUE, zscale=50, theta=-45,
waterdepth = 0, wateralpha = 0.6, watercolor = "#88DDFF",
waterlinecolor = "white", waterlinealpha = 0.5)