3-D shadow maps in R: the rayshader package

September 26, 2018
By

(This article was first published on Revolutions, and kindly contributed to R-bloggers)

Data scientists often work with geographic data that needs to be visualized on a map, and sometimes the maps themselves are the data. The data is often located in two-dimensional space (latitude and longitude), but for some applications we have a third dimension as well: elevation. We could represent the elevations using contours, color, or 3-D perspective, but with the new rayshader package for R by Tyler Morgan-Wall, it's easy to visualize such maps as 3-D relief maps complete with shadows, perspective and depth of field:

Tyler describes the rayshader package in a gorgeous blog post: his goal was to generate 3-D representations of landscape data that "looked like a paper weight". (Incidentally, you can use this package to produce actual paper weights with 3-D printing.) To this end, he went beyond simply visualizing a 3-D surface in rgl and added a rectangular "base" to the surface as well as shadows cast by the geographic features. He also added support for detecting (or specifying) a water level: useful for representing lakes or oceans (like the map of the Monterey submarine canyon shown below) and for visualizing the effect of changing water levels like this animation of draining Lake Mead.

Raytracer

The rayshader package is implemented as an independent R package; it doesn't require any external 3-D graphics software to work. Not only does that make it easy to install and use, but it also means that the underlying computations are available for specialized data analysis tasks. For example, research analyst David Waldran used a LIDAR scan of downtown Indianapolis to create (with the lidR package) a 3-D map of the buildings, and then used the ray_shade function to simulate the shadows cast by the buildings at various times during a winter's day. Averaging those shadows yields this map of the shadiest winter spots in Indianapolis:

Indianapolis Winter

The rayshader package is available for download now from your local CRAN mirror. You can also find an overview, and the latest version of the package at the Github repository linked below.

Github (tylermorganwall): rayshader, R Package for Producing and Visualizing Hillshaded Maps from Elevation Matrices, in 2D and 3D

 

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