Well, PF doesn't have relative lighting rules, and certainly nothing about adaptive night vision.
You're right! Nor does it have rules for the acceleration due to gravity, the nutritional value of bread or the alcohol content of wine. However, I guess we would all assume that those things all work as in our common observed experience? Are you doubting the existence of shadows (a common relative lighting experience) in PF?![]()
Are you prepared to rule how everything about everything works? How much bearing do these things have at the level of resolution we are looking at? How do they interact with other parts of the rules?
Naturally, I am familiar with shadows, a phenomen that produces relatively dim light. Does everything in a shadow benefit from concealment?
My point is, "This basically makes sense to me," is a fine standpoint to make many rulings, but "This is the rule, which comfortably interacts with the rest of the system" is another important design consideration. For instance, suppose you decided it was realistic for a coup de grace to reliably kill any human being. Ok, what about doing it under fire from arrows? What about an ogre? ... a giant? Is a Huge Titan subject to being automatically killed? So if you are having a problem with characters surviving deadly attacks while helpless, it is useful to devise a general mechanic, as the d20 rules and PF have done, that quantifies what is supposed to happen.
Since a rule already addresses concealment and sneak attack, I would like to find some way to work within that system. Hand-waving is okay, but in this situation not ideal, from my standpoint.
The Most Important Rule
The rules in this book are here to help you breathe life into your characters and the world they explore. While they are designed to make your game easy and exciting, you might find that some of them do not suit the style of play that your
gaming group enjoys. Remember that these rules are yours. You can change them to fit your needs.
That won't work unless your the DM: you can't force the DM to change the ruleds to let your sneak attack if he thinks shadows provide concealment.
That rule isn't helpful unless you DM the game.
Looking out of my window now - I can see a person sitting on a bench in sunlight and a person near them in the shade. It appears that shadows do not always provide concealment. I imagine you could perform this empirical test as a thought experiment using your knowledge of the world and arrive at the same conclusion.
No, but having rules that you can point to as the actual rules does give more willingness to a DM to use.
Same reason DMs are wary of homebrewed class because they aren't of the rules. The DM isn't sure if it will mess with balance.