Vision

let rating = origin.system.technology.rating; /* For most technological sources. */
let rating = actor.system.attributes.magic.value; /* For adept and critter powers. */
let rating = 6; /* You can also set a static value, for natural senses or special cases. */
/* Only use one of above. */

token.document.update(
{ sight:
  { color: "#004422",
    range: (rating / 2 + 3) ** 2, /* Low-Light Vision */
    range: (rating / 2 + 1) ** 2 /* Thermographic Vision */
    /* Only use one of above. */
    angle: 360
  }
});