Problem with `terra::shade`: Neighborhood size parameter for hill shade algorithm?

The terra::shade hill shade algorithm only uses immediate neighbors to compute hill shading. In contrast, Google Earth Engine's ee.Algorithms.HillShadow has a neighborhood size argument, which can lead to very different results. Below is a minimal reproducible example that shows how terra::shade only casts shadows in the immediate vicinity of the "tower" in the middle. Using the same raster, GEE's ee.Algorithms.HillShadow produces very different results (see figure and code).

I am also including plots from a real-world example based on a high-resolution digital surface model. This illustrates the difference in a real-world application of the algorithm.

Question

What are options for a hillshade algorithm in R that take a larger neighborhood size into account similar to GEE's ee.Algorithms.HillShadow?

R Code

library("tidyverse") library("terra") library("tidyterra") library("ggpubr") # Define raster set.seed(123423) dsm_values <- sample(1:3, 1000, replace = TRUE) m <- matrix(dsm_values, nrow = 100, ncol = 100) m[40:60,40:60] <- 100 r <- rast(m, crs = "epsg:2263") names(r) <- "dsm" # Compute hillshade terrain <- terra::terrain(r$dsm, c("slope", "aspect"), unit = "radians") shade <- terra::shade(terrain$slope, terrain$aspect, angle = altitude, direction = azimuth, normalize = TRUE) g1 <- ggplot() + geom_spatraster(data = r, aes(fill = dsm)) + scale_fill_gradientn(colors = c('blue', 'limegreen', 'yellow', 'darkorange', 'red')) + ggtitle("DSM") + theme_bw() g2 <- ggplot() + geom_spatraster(data = shade, aes(fill = hillshade)) + scale_fill_gradient2(low = "#ffffff", high = "#000000") + ggtitle("shade") + theme_bw() ggarrange(g1, g2) 

GEE

// IMPORT raster as `dsm` var azimuth = 136; var altitude = 14.6; /* Shadow ----------------------------------------------- */ var shade = ee.Algorithms.HillShadow(dsm, azimuth, altitude, 300); /* Mapping shadow ---------------------------- */ Map.centerObject(dsm, 18); var params = {min: -5, max: 500, palette: ['blue', 'limegreen', 'yellow', 'darkorange', 'red']}; Map.addLayer(dsm, params, 'DSM', true); Map.addLayer(shade, {min:0, max: 1, palette: "black, white"}, 'Shadow', true, 0.5); 

terra::shade

GEE ee.Algorithms.HillShadow

Real-world example