Example code to great a hillshade raster from a DEM in R using spherical environment mapping for the colour scheme.

sph_hillshade.r

library(raster)
library(jpeg)

# Spherical environment mapping hillshade function
getv=function(i,a,s){
  ct = dim(i)[1:2]/2
  sx = values(s)/90 * ct[1]
  sy = values(s)/90 * ct[2]
  a = values(a) * 0.01745
  px = floor(ct[1] + sx * -sin(a))
  py = floor(ct[2] + sy * cos(a))
  
  
  template = brick(s,s,s)
  values(template)=NA
  
  cellr = px + py * ct[1]*2
  cellg = px + py * ct[1]*2 + (ct[1]*2*ct[2]*2)
  cellb = px + py * ct[1]*2 + 2*(ct[1]*2*ct[2]*2)
  
  template[[1]] = i[cellr]
  template[[2]] = i[cellg]
  template[[3]] = i[cellb]
  
  template = template * 256
  
  template
}

# Load a digital elevation raster 
# An example can be found here: https://www.dropbox.com/s/utup77tpyrioqio/dem.tif?dl=0
dem = raster("dem.tif")

# Generate slope and aspect rasters
slope=terrain(dem,opt='slope',unit='degrees')
aspect=terrain(dem,opt='aspect',unit='degrees')

# Load an environment map image
# An example can be found at http://i.imgur.com/9pvbHjN.jpg
map=readJPEG("9pvbHjN.jpg")

# Do the mapping
out = getv(map, aspect, slope)

# Plot pretty mountains
plotRGB(out)