Unknown Ranges and Threatened Tiles

[Brutter]

So, the standard rules for attacking and/or threatening a tile with a melee weapon, for Medium characters, state that you normally threaten 5 ft away from you in any direction. Unless you're using a reach weapon in which case you no longer threaten the 5 ft tiles, and instead threaten 10 ft tiles. Unless you are using a spiked chain or other weapon that threatens both 5 ft and 10 ft away from you. Unless you are using the whip, which can be used to hit anything within 15 ft, but you don't threaten any of the squares.

My question, then, is what happens when you have a weapon that has a different reach than standard weapons, and doesn't specify which tiles can be attacked or not. If there is another weapon with a 15 ft range, can it attack any tile within that range, like the whip? Presumably it would threaten all those squares as well. And, given that we have examples of 10 ft weapons that both can and can't be used within 5 ft, what are we to assume when something simply has a 10 ft range? Normally, they would try to specify, but with the number of sourcebooks written by various people, you can never count on clarity.

What if there is some way to get a 20 ft range on a melee weapon for a medium character? There probably is, somewhere in the game. If I come across it, I want to know what to expect my threatened tiles could be. I could see an argument for any possible range of tiles, provided it caps at 20 ft and doesn't have a gap in the middle.

[BowStreetRunner]

Can you provide an example? Because I honestly can't think of any.

Normally, weapon size is irrelevant to the concept of reach. Instead, it is a special property that some weapons explicitly have and all other weapons don't. IRL a halberd and a glaive might be about the same size, but in the game a glaive has reach because it says it does and a halberd doesn't have reach because it doesn't say it does. The other element of reach has to do with the creature and its size - not the weapon size. So if a creature has reach it has reach with any weapon, not just a reach weapon. But if a smaller creature uses a weapon of a larger size it doesn't get reach just because the weapon is larger. It would only get reach if the weapon was explicitly a reach weapon.

[Brutter]

Can you provide an example? Because I honestly can't think of any.
Well the point of the question is to find the general rule, not a specific example. In general, if there's a weapon with a 15-foot reach, what tiles does that weapon threaten? I looked through some of the sourcebooks for whip-like weapons. and I found a great example. The Spell Compendium's Flame Whips spell. It specifies that "you gain two melee touch attacks with a 15-foot reach", and that's it. But what does a "15-foot reach" mean, in a game with so many contradictory reach rules for specific weapons?

You'd think, since it says "Whips" and has the same range as a whip, it can hit all the same tiles a whip can, which is why I don't think it's the best example to use in this argument. My goal is to find a general rule for any melee attack that works within a certain range, not theorise about whip-like weapons and their attack ranges.

[Deophaun]

First: Reach is for melee attacks. Range is for ranged attacks.

Reach is first and foremost defined by the creature. However, there is also a weapon property called reach that doubles the reach of the creature that wields it for the purpose of threatening squares and attacking with the weapon, regardless of the weapon's size. To further the confusion, occasionally weapons will have a specific reach, such as the whip's 15', which means it can only attack up to 15' away from the creature wielding it, regardless of the creature's size.

[BowStreetRunner]

The general rule for reach weapons (http://www.d20srd.org/srd/equipment/weapons.htm#reachWeapons) is that their natural reach is doubled, meaning that a natural reach of 5 ft becomes a reach of 10 ft (and they cannot attack at 5 ft) while a natural reach of 5 and 10 ft becomes a reach of 15 and 20 ft (but not 5 and 10 ft). So you can no longer reach things you could before, but you can now reach things twice as far away as before. Any exception to this general rule will be spelled out in the description of the specific weapon (whip, spiked chain, etc.).

[zlefin]

the pathfinder rules are largely the same, so I'd use those templates for threatened tiles found here:
https://www.d20pfsrd.com/gamemastering/combat/space-reach-threatened-area-templates/

the only difference i'm aware of (which I only found out by looking) is a special rule in 3.5 that medium creatures' reach weapons threaten the square 2 diagonals away from them, despite that normally being 15', that's done so you can't move next to a reach user via the diagonal to avoid the AoO.
for some reason that tidbit wasn't ported to pathfinder.
thread discussing this anomaly:
http://paizo.com/threads/rzs2lost?Reach-at-diagonals

[KillianHawkeye]

Note that whips, despite the unusual 15-foot reach, don't threaten the area you can attack into. In 3.0 rules, they actually operated more like a hand-held ranged weapon.

[liquidformat]

First an interesting weapon for this conversation, the sky lance, I want to say it is in Champions of Valor but will have to check has 30' reach if I remember correctly but I don't know if it threatens squares.

Second, for ranged weapons with creatures that have reach, does the creature add on an extra 5' for the first range increment due to their reach or effectively is an ogre throwing a throwing axe 10'/ the same distance it can reach?...

[Deophaun]

It would be throwing the same distance it can reach. There's no interaction between reach and range.

[tyckspoon]

What if there is some way to get a 20 ft range on a melee weapon for a medium character? There probably is, somewhere in the game. If I come across it, I want to know what to expect my threatened tiles could be. I could see an argument for any possible range of tiles, provided it caps at 20 ft and doesn't have a gap in the middle.

To start with, there is a distinction between reach and using a reach weapon. Using a reach weapon modifies the wielder's normal reach. So a standard Medium creature has a 5-foot reach; they threaten and can attack squares within 5 feet of them. A standard Large creature has a 10-foot reach; they threaten and can attack any squares within 10 feet of them. The standard rule for a reach weapon is to double the creature's regular reach, and then remove the original. A Medium creature with a reach weapon threatens and can attack squares 5 to 10 feet away from them, but no longer threatens those within 5 feet. A Large creature with a reach weapon threatens and can attack 10 to 20 feet away, but no longer threatens those within 10 feet. Exceptions to that for reach weapons need to be called out for the specific weapon, as it is for the Spiked Chain. If a weapon is marked as Reach (this is a special quality of the weapon and will be marked the same way as it would for a weapon that gets special bonuses to Tripping or Disarming), then it is subject to the 'donut hole' unless otherwise stated.

If you get reach extensions, it still works that way - a Medium creature that has found a way to get +5 foot reach threatens and attacks into squares up to 10 feet away. If he wields a reach weapon, double his reach and subtract the donut; he threatens and attacks 10 to 20 feet away, but no longer threatens 0 to 10 feet away.

If a weapon or effect just specifies a reach, ignore all of the above and just use that reach. It'll work like natural reach (threatens and can attack into all squares within that reach) unless the effect says otherwise. Your example Flame Whips would work like that - regardless of the user's natural reach, weapons, or other abilities that affect their reach, they threaten and can attack all squares up to 15 feet away.

If a weapon actually says it has a range, ignore all of the above. Range is a property of missile weapons and thrown weapons and does not have anything to do with reach at all.