add_shadow(hillshade, shadowmap, max_darken = 0.7)

## Arguments

hillshade A three-dimensional RGB array or 2D matrix of shadow intensities. A matrix that incidates the intensity of the shadow at that point. 0 is full darkness, 1 is full light. Default 0.7. The lower limit for how much the image will be darkened. 0 is completely black, 1 means the shadow map will have no effect.

## Examples

#Raytrace the volcano elevation map and add that shadow to the output of sphere_shade()

volcano %>%
plot_map()
#Increase the intensity of the shadow:
volcano %>%
plot_map()