How to get a dull and shadowed mesh with rgl?

Below are two meshes of the Barth sextic. The first one is obtained with the R package rgl. It is rather shiny and it has almost no shadow. The second one is obtained with the Haskell package OpenGL. It is dull and shadowed.

I'd like to know how to obtain a rendering similar to the Haskell one with rgl? As far as I know, both libraries are wrapper of openGL, so that should be possible.

# isosurface f=0
phi <- (1 + sqrt(5)) / 2
f <- function(x, y, z){
  4 * (phi^2*x^2 - y^2) * (phi^2*y^2 - z^2) * (phi^2*z^2 - x^2) - 
    (1 + 2*phi) * (x^2 + y^2 + z^2 - 1)^2
}
# make the isosurface
nx <- 220L; ny <- 220L; nz <- 220L
x <- seq(-1.8, 1.8, length.out = nx) 
y <- seq(-1.8, 1.8, length.out = ny)
z <- seq(-1.8, 1.8, length.out = nz) 
Grid <- expand.grid(X = x, Y = y, Z = z)
voxel <- array(with(Grid, f(X, Y, Z)), dim = c(nx, ny, nz))
mask  <- array(with(Grid, X^2 + Y^2 + Z^2 > 3), dim = c(nx, ny, nz))
voxel[mask] <- -1000
library(rmarchingcubes)
cont <- contour3d(voxel, level = 0, x = x, y = y, z = z)
# plot
library(rgl)
mesh <- tmesh3d(
  vertices = t(cont[["vertices"]]),
  indices  = t(cont[["triangles"]]),
  normals  = cont[["normals"]],
  homogeneous = FALSE
)
#
open3d(windowRect = c(50, 50, 562, 562), zoom = 0.65)
shade3d(mesh, color = "#ff00ff")

The (unique) light in the Haskell scene is located at (-50, 100, 100) and has colors ambient=black, diffuse=white, specular=white.

I think I get it. One has to clear the default lighting first, then add a light like the one in the Haskell scene. I also set the specular color of the mesh to black.

open3d(windowRect = c(50, 50, 562, 562), zoom = 0.65)
clear3d(type = "lights")
light3d(x = -50, y = 100, z = 100, ambient = "black")
shade3d(mesh, color = "#ff00ff", specular = "black")