使用r函数persp3d时，我看不到3D数字

Question

使用R函数persp3D时，我看不到3D数字，例如使用此演示代码，它不会显示Andy 3D图，是因为R的版本吗？

# (1) The Obligatory Mathematical surface.
#     Rotated sinc function.

x <- seq(-10, 10, length = 20)
y <- x
f <- function(x, y) { r <- sqrt(x^2 + y^2); 10 * sin(r)/r }
z <- outer(x, y, f)
z[is.na(z)] <- 1
open3d()

# Draw the surface twice:  the first draws the solid part, 
# the second draws the grid.  Offset the first so it doesn't
# obscure the lines.

persp3d(x, y, z, aspect = c(1, 1, 0.5), col = "lightblue",
        xlab = "X", ylab = "Y", zlab = "Sinc( r )", 
        polygon_offset = 1)
persp3d(x, y, z, front = "lines", back = "lines", 
        lit = FALSE, add = TRUE)
highlevel()   # trigger the plot