Set the 3D viewpoint of an RGL window using anatomical terms
nview3d(
  viewpoint = c("frontal", "anterior", "dorsal", "ventral", "posterior", "left",
    "right", "oblique_right", "oblique_left"),
  FOV = 0,
  extramat = NULL,
  ...
)# \donttest{
plot3d(kcs20, soma=TRUE)
nview3d('frontal')
nview3d('ant')
nview3d()
nview3d('posterior')
nview3d('oblique_right')
# a slightly oblique frontal view
nview3d('frontal', extramat=rotationMatrix(pi/10, 1, 1, 0))
# }