Calculates a shadow for each point on the surface using the method described by Leland Brown in "Texture Shading: A New Technique for Depicting Terrain Relief."

texture_shade(
  heightmap,
  detail = 0.5,
  contrast = 1,
  brightness = 0,
  transform = TRUE,
  dx = 1,
  dy = 1,
  pad = 50
)

Arguments

heightmap

A two-dimensional matrix, where each entry in the matrix is the elevation at that point.

detail

Default `0.5`. Amount of detail in texture shading algorithm. `0` is the least detail, while `1` is the most.

contrast

Default `1`,standard brightness. Amount of contrast in the texture shading. This transforms the resulting darkness using the formula `tanh(input * contrast + brightness)`.

brightness

Default `0`, standard brightness. Higher values will brighten the texture hillshade, while lower values will darken it.

transform

Default `TRUE`. Whether to apply the `tanh(input * contrast + brightness)` transformation. This transforms the resulting darkness using the formula `tanh(input * contrast + brightness)`.

dx

Default `1`. The distance between each row of data (compared to the height axis).

dy

Default `1`. The distance between each column of data (compared to the height axis).

pad

Default `50`. The amount to pad the heightmap so edge effects don't appear from the fourier transform. Only increase this if you encounter boundary effects.

Value

2D matrix of hillshade values.

Examples

#Create a direct mapping of elevation to color:
# \donttest{

#Plut using default values
montereybay %>% 
  texture_shade() %>% 
  plot_map()

  
#Increase the level of detail
montereybay %>% 
  texture_shade(detail=1) %>% 
  plot_map()

  
#Decrease the level of detail
montereybay %>% 
  texture_shade(detail=0) %>% 
  plot_map()

  
#Increase the level of contrast
montereybay %>% 
  texture_shade(contrast=3) %>% 
  plot_map()

  
#Increase the brightness for this level of contrast
montereybay %>% 
  texture_shade(contrast=5, brightness = 2) %>% 
  plot_map()

  
#Add a texture_shade() layer into a map
montbay = montereybay
montbay[montbay < 0] = 0

montbay %>%
  height_shade() %>%
  add_water(detect_water(montbay), color="dodgerblue") %>%
  add_shadow(texture_shade(montbay, detail=1/3, contrast = 5, brightness = 6),0) %>%
  add_shadow(lamb_shade(montbay,zscale=50),0) %>% 
  plot_map()

# }