LoS

Wargame rules often spend a fair number of paragraphs on who can see whom. Line of sight - usually abbreviated LoS - can be a part of everything from firing weapons to charging to a commander changing a unit's orders, so wargames treat it with some care. Fans of the original Squad Leader will remember the dot in the center of each hex used for determining whether a particular hex could be seen from another hex, or the determination of "hull down" for AFVs on ridgelines.

After wargames birthed roleplaying games, the need to determine when something was in view to the characters remained. OD&D, for instance, says that monsters are detected at a distance of 20-80 feet underground or 40-240 yards outdoors unless the party is surprised. It's interesting there's no consideration for individual character proficiency, and when such a differentiation appears, it's associated with classes and skills, not ability scores. Frex, the 1e AD&D Ranger, as a class ability, is more likely to surprise an opponent and less likely to be surprised in turn, while in Traveller, the Tactics and Leader skills and military experience favorably modify surprise for the adventurers.

Boot Hill retains a facing system more like that of the tabletop miniature skirmish game from which it was derived, with characters able to observe a 90-degree arc ahead of them and the ability to observe someone in concealment wholly at referee discretion. I soon added a house rule that a character could spend one movement point to 'look around,' which allowed the character to extend the observation axis by another 90-degrees to the left or right; in this way, a character could run but would be slowed by taking his attention off the direction in which he was moving, which seemed a fair trade-off. Again, the character's attributes played no particular role in determining what could be seen, and in BH, even the dice were removed as a factor, as opposed to D&D or Traveller.

It wasn't too many years before roleplaying games introduced rules for alertness, perception or observation, often associated with a character attribute and/or skill, and this soon became the norm; with some games, such as d20-based systems, a combination of attribute scores, skill points, and feats could produce 'Spot-monkeys' with superhuman powers of observation.

Though I think that later roleplaying games tend to make too big a deal out of things like Spot, Alertness, and so forth, treating all characters as equally perceptive is perhaps a bit too coarse-grained as well, appropriate to small units but not distinct individuals. Accordingly, for my Flashing Blades campaign, I use a blending of the two methods. The core rules make no mention of surprise or observation, but examples in the published adventures point to both the Wit and Luck attributes; in fact, it was this usage of Luck that led me to spell out that in my campaign, Luck is, "rather than a metaphysical force or quality, the insightfulness of the character: it's the ability to notice subtle clues or behaviors, to be in tune with one's surroundings" - a gambler, for which Luck is the associated attribute, isn't so much smiled upon by Fortune as he is able to pick up tells from his fellow gamblers, for example. As such, Luck is often used to represent the power of observation or perception in actual play.

As a modifier to an individual's Luck attribute, I also use the combined surprise and initiative rules for original, 'classic' Traveller - the skills Captaincy and Strategy replace Traveller's Leader and Tactics respectively, and service on a campaign gives the benefit of military experience. If the adventurers are surprised as a group, then individual Luck checks are made at a penalty of Luck/2 or Luck/3 at my discretion. For me this achieves the best of both worlds.