Spell Interruption Rate

[Septimus]

I personally cant't recall being interrupted by a hit from any mob (not even something like Tiamat's non flying hits) when Stoneskin absorbed the whole damage of the hit (I'm not saying it's not possible, just that if it is it's really rare). It's certainly possible that a different criteria applies if you take 0 damage than when you take >0 damage.

I am fairly certain that you have to take damage from a hit (or get knocked back/stunned) for it to interrupt casting. I solo a lot, I never have to worry about recasting Ninjutsu with skill capped at level 36 when I have stoneskin up. (Generally a light breeze can interrupt that.)

[Fryte]

From what I noticed, when Stoneskin breaks it acts if the whole hit landed for damage in regards to interrupt.

[Okuza]

One of the issues has to do with latency between client and server. Basically, your client doesn't register you've been hit until a certain period of time after the server says you have, and the server doesn't know you're casting a spell until that same period of time after you initiate the cast. Often, in times of high lag/latency/etc, you'll notice a cast will go through even though you've been hit after the 20% mark, or you'll get interrupted even though you got hit when/after the spell should have taken effect.

Someone always brings up latency. Network latency pretty much doesn't exist on the human-noticeable level; I have about 500ms total maximum latency between me and FFXI servers (round trip) on a really bad day. Typically it's down around 220ms. That's only 10% of the total cast time for utsusemi:ni (5% either side) and a lot less for longer spells. More significant is the server-side lag, which can be longer than the cast time of a spell if it's as crowded as Besieged. Server latency still doesn't explain the 80/20 non-interrupt zone, though -- not even close.

The best example of 80/20 non-interrupt I know is Teleport-XXX punting; eg. cast Teleport-Holla on group, then zone into your mog house. I start running at around 72-73% on my whm. Spell isn't interrupted, but still goes off. Teleport spells have a 20s cast time. 20% is 8s. There is not 7.5s of lag on the server. Considering human reaction time differential between me seeing it at 72 and moving the character and the server noticing the character is moving, that could very well be as much as 8% (1.6s), which puts the teleport into the non-interruptible zone and thus why it fires off even when the spell caster is safely inside of the MH.

I do happen to like the side-extension theory for interrupts, but I'm not married to the idea. I think interrupts are more complex than explained by that. For instance, I've never ever been interrupted when I take zero damage from a hit -- not even if it was a critical hit (eg. absorbed by SS). And, after increasing ninjutsu skill, I felt like interrupts were less frequent. Same with after altering macros to pop on non-blinking +skill gear during utsu casting.

My guess/hunch on how %interrupt gear works is that it's not %-additive, but an actual real percent; eg. +10% gear gets you 78/22% on the sides and a bit of an extra boost over the base chance in the middle. Perhaps by just boosting your skill a little in the test, perhaps by other methods. This is why with even a ton of %interrupt gear, you still get interrupted when hit in the middle and nin or sub/nin tanks still have to time their utsu casts to the hits.

[Ferien]

I wasn't talking about the 80/20 zone, I'm well aware of that one, considering I played PLD before Shield Mastery existed. I'm talking about the times when you'll get a spell off even though you get smacked hard at 50~60%, or the times when you get hit at 85~90% and the spell stops. It happens, but only when there's massive amounts of latency and/or lag.

If spells were interruptible between 0~20% and 80~100%, PLDs wouldn't be able to get Cure4 off, and noone would be able to cast Utsu:Ichi while being attacked. The zone obviously exists, and is necessary for much of how we play the game.

[Metah]

I can get hit for 200 dead in the middle of a spell on RDM (That I have native skill in) and not get interrupted, but I can get hit for 1 from an IT and interrupt almost every time. I doubt it has anything to do with the amount of damage. I think it's a skill to skill comparison just like ACC and EVA, ATK and DEF, STR and VIT, etc. Weapon Skill vs Magic Skill.

As far as what the gear does, I'm siding with the "Window" theory myself.

Level differences would play a big part in that regard as well, eh?

[Sylvrdragon]

I can get hit for 200 dead in the middle of a spell on RDM (That I have native skill in) and not get interrupted, but I can get hit for 1 from an IT and interrupt almost every time. I doubt it has anything to do with the amount of damage. I think it's a skill to skill comparison just like ACC and EVA, ATK and DEF, STR and VIT, etc. Weapon Skill vs Magic Skill.

As far as what the gear does, I'm siding with the "Window" theory myself.

Level differences would play a big part in that regard as well, eh?

That's what I meant to say, that should be "...hit for 200 by an EP in the middle...", but I think faster than I type, so I have a tendency to leave out words on occasion. <.<

[cassiraa]

Also remember, that the spell interruption check happens when the mob STARTS it's attack animation, not when the animation hits you. On slow attacking mobs, you can get double attacked and hit at 40% and 60% and not get interrupted if you started casting after the mob's idle animation turned into it's attack animation.