How does trip work

[Thac0 Redeye]

More so than just the process of hit, check...etc. what are the actual mechanics? Here's my situation. In out party is a goliath barbarian who has imp trip and a spike chain. Last week we had an encounter in a crypt against a vampire spawn. During one turn the vamp was on one end of a 5x10' casket, next to him was the dwarf fighter (also on the casket) and on the ground next to the dwarf was the goliath. All in a row. The goliath wanted to trip the vamp because he has reach. (through the dwarf). So my question when he trips does the chain sweep across the legs like a karate leg sweep or does it flick and wrap around an ankle and pull? Should he be able to trip around an ally? I said no as the DM but got a lot of backlash from players because he has reach.
Thanks

Also on a second note....he has a BAB of 8. (2 attacks/round on full attack action) if there is 2 enemies in front of the goliath can he trip/attack against both as his full round attack?

[Telonius]

More so than just the process of hit, check...etc. what are the actual mechanics? Here's my situation. In out party is a goliath barbarian who has imp trip and a spike chain. Last week we had an encounter in a crypt against a vampire spawn. During one turn the vamp was on one end of a 5x10' casket, next to him was the dwarf fighter (also on the casket) and on the ground next to the dwarf was the goliath. All in a row. The goliath wanted to trip the vamp because he has reach. (through the dwarf). So my question when he trips does the chain sweep across the legs like a karate leg sweep or does it flick and wrap around an ankle and pull? Should he be able to trip around an ally? I said no as the DM but got a lot of backlash from players because he has reach.
Thanks

Also on a second note....he has a BAB of 8. (2 attacks/round on full attack action) if there is 2 enemies in front of the goliath can he trip/attack against both as his full round attack?

If you're trying to figure out the physics of how a spiked chain would actually look, the answer is "a wizard did it." The weapon is silly and (at least as it's pictured in the PHB) wouldn't actually work. It's one of those things that you just have to pretend will work the way the rules say it ought to.

As for tripping around an ally, this would be handled by the Cover (https://www.d20srd.org/srd/combat/combatModifiers.htm#cover) rules:


When making a melee attack against a target that isn’t adjacent to you (such as with a reach weapon), use the rules for determining cover from ranged attacks.

For ranged attacks:

To determine whether your target has cover from your ranged attack, choose a corner of your square. If any line from this corner to any corner of the target’s square passes through a square or border that blocks line of effect or provides cover, or through a square occupied by a creature, the target has cover (+4 to AC).

There's no solid barrier (like a wall) between the goliath and the vampire spawn, so they have line of effect.

The dwarf is standing directly between the goliath and the vampire spawn, so the line passes through a square occupied by a creature. The target has cover versus the Goliath's attack, gaining +4 to AC. The Goliath can try to do a Trip attempt, it's just going to be more difficult.

There is one other option, that you as the DM would have to determine; if the setup gives the target "Improved Cover":


Varying Degrees of Cover
In some cases, cover may provide a greater bonus to AC and Reflex saves. In such situations the normal cover bonuses to AC and Reflex saves can be doubled (to +8 and +4, respectively). A creature with this improved cover effectively gains improved evasion against any attack to which the Reflex save bonus applies. Furthermore, improved cover provides a +10 bonus on Hide checks.

How exactly you determine that isn't spelled out in the rules. Personally I think it was intended for things like, attacking through a grate or a portcullis, something like that. It gives you an out for any kind of weird exception where you'd think, "Yeah, I guess that could hit, but it's gonna be real hard." In this case you're attacking from lower ground; I'm not sure that I'd say that's enough to qualify, but as the DM it's your call.


EDIT: For the second part of your question, here's the text from Improved Trip (https://www.d20srd.org/srd/feats.htm#improvedTrip):


If you trip an opponent in melee combat, you immediately get a melee attack against that opponent as if you hadn’t used your attack for the trip attempt.

So, yes; with Improved Trip and an iterative attack, you can potentially do a "Trip/Attack - Trip/Attack" routine every round, as long as enemies are in range, and he decides that he wants to. (He might not bother if it's a Huge opponent, but it's often a good bet against same-sized or smaller). This is one of the reasons that Trip-based melee combatants with reach weapons are seen as a good tactical option. With reach, usually more enemies are in your threat range, and vulnerable to being tripped. The downside is that if the trip attempt fails, he's both vulnerable to being tripped himself, and the enemy is still standing up and has taken no damage.

[Kurald Galain]

The way this could work is that the PCs, being teammates, have agreed on a quick code word that the barb shouts, and then the dwarf jumps and the chain can go underneath him. That's still harder, hence the -4.


Also on a second note....he has a BAB of 8. (2 attacks/round on full attack action) if there is 2 enemies in front of the goliath can he trip/attack against both as his full round attack?
Yes.

[KillianHawkeye]

So my question when he trips does the chain sweep across the legs like a karate leg sweep or does it flick and wrap around an ankle and pull?

Honestly, it could be either of those or something else. How you describe it isn't really important to how it works as a game mechanic, just like how you don't have to describe exactly how you're hitting an orc with your sword.

[Biggus]

How exactly you determine that isn't spelled out in the rules. Personally I think it was intended for things like, attacking through a grate or a portcullis, something like that. It gives you an out for any kind of weird exception where you'd think, "Yeah, I guess that could hit, but it's gonna be real hard." In this case you're attacking from lower ground; I'm not sure that I'd say that's enough to qualify, but as the DM it's your call.


The PHB says:



In some cases, cover can provide a greater bonus to AC and Reflex saves. For instance, a creature peering around a corner or through an arrow slit has even better cover than a creature standing behind a low wall or an obstacle. In such situations, the DM can double the normal cover bonuses to AC and Reflex saves.

This is pretty similar to in 3.0, where what's just called cover in 3.5 was called one-half cover, and there was also three-quarters cover and nine-tenths cover, which gave similar bonuses to what's now called improved cover.