I'd say you'd need a more realistic health/damage system in order to have a realistic regen/rest system. Because health is defined very abstractly in most games - in fact, it's often referred to as "hit points," which delineates a difference from just plain "health." Hit points really can represent anything from light bleeding to fighter's initiative/stamina to severe wounds, etc., etc. And yet even if you specify that hit points mean only a pool of health, that itself is not even a realistic model (as in a fight you don't seek to whittle down health but whittle down stamina, and strike critical hits at the health of their body in order to disable and not whittle), so how would you even define what realistic regeneration of an unrealistic model is?
Whereas if you intentionally go with a more specific and less abstract model, like a wounds model, then you can better define how you should go about handling regeneration.
This also ties into encounter design. In that typical RPGs throw so many trash encounters at you to the point where it's unrealistic to expect any "real" party to survive the attrition. In which case, an unrealistic resting model simply balances out against the unrealistic encounter difficulty.
Edit: I thought of one way to work this through an abstract hp system though... Simply, keep track of how much damage each discrete attack does on the character. Low damage hits could be considered 'bleeding' or 'nicking' cuts, which can be regened at rest. High damage hits could be considered wounding at not regenerated at rest. Complexify this as you will.
Actually on second thought this would not be too hard to calculate in a game. Simply have a "bleeding" (or other low damage) pool that is stored as you take damage. When you rest, you can regenerate as much hp as in your "bleeding pool" and no more. Something like that. No need to keep track of high damage hits.
And on third thought, if the "bleeding pool" could be regenerated in-combat (via some unmentioned mechanic), then it would offer a tactical benefit to trying to do high damage critical hits in order to maim, rather than simply bleed and let the enemy recover.
I think that's better than a simple threshold, because a threshold doesn't allow for a distribution of a variety of types of damaging hits.
Whereas if you intentionally go with a more specific and less abstract model, like a wounds model, then you can better define how you should go about handling regeneration.
This also ties into encounter design. In that typical RPGs throw so many trash encounters at you to the point where it's unrealistic to expect any "real" party to survive the attrition. In which case, an unrealistic resting model simply balances out against the unrealistic encounter difficulty.
Edit: I thought of one way to work this through an abstract hp system though... Simply, keep track of how much damage each discrete attack does on the character. Low damage hits could be considered 'bleeding' or 'nicking' cuts, which can be regened at rest. High damage hits could be considered wounding at not regenerated at rest. Complexify this as you will.
Actually on second thought this would not be too hard to calculate in a game. Simply have a "bleeding" (or other low damage) pool that is stored as you take damage. When you rest, you can regenerate as much hp as in your "bleeding pool" and no more. Something like that. No need to keep track of high damage hits.
And on third thought, if the "bleeding pool" could be regenerated in-combat (via some unmentioned mechanic), then it would offer a tactical benefit to trying to do high damage critical hits in order to maim, rather than simply bleed and let the enemy recover.
I think that's better than a simple threshold, because a threshold doesn't allow for a distribution of a variety of types of damaging hits.
