def sinebow(h):
  """A cyclic and uniform colormap, see http://basecase.org/env/on-rainbows."""
  f = lambda x: jnp.sin(jnp.pi * x)**2
  return jnp.stack([f(3 / 6 - h), f(5 / 6 - h), f(7 / 6 - h)], -1)