Spell Interruption Rate: Theory and Modeling

[Elesirdur]

Program modeling geeks come on in.

While finally leveling Ninja my interest in understanding Spell Interruption Rate has been piqued and I'm wanting to know more about how the game handles this combat function. I never really paid much attention to this while leveing Paladin. Curing was simple, just get the spell off between the mobs delay period and you'll be fine. However, with Utsusemi's longer cast period coming to grips with Spell Interruption Rate is more important.

The only major source I've found explaning spell int. rate is over at FFXIclopedia but the static reasoning based on damage, casting skill, and mob dificulty doesn't seem to totally mesh with my own observations during play. According to their theory, a hit any time during the casting period has a chance of interrupting one's casting. And it certainly is true in my experience that lower lvl mobs and low damage hits are far less likely to interrupt a casting than a high damage hit by a difficult mob.

What I'm seeking to understand is the range in which one is still able to get hit during the casting period. I've observed that from roughly 0-30% and 80-100% of the casting period I can take a full-strength hit and still have my ninjitsu go off. Taking damage during the 31-79% casting period will result in an iterruption. From these observations it would appear that Spell Interruption Rates are based on a bell curve-like model with lower chances of interruption ocurring at the extremes and the highest chance of interruption during the media phase.

If we accept that model as true then how does an item that offers a Spell Interruption Rate decrease bonus modify the model. Take the Nikkariaoe which offeres Spell Interruption Rate -25%. Does this modifier reduce the interruption rate 25% across the entire curve or does it decrease the period in which one is interrupted when hit? Using the above period of 31-79% casting range, a 25% reduction would create an interruption period of 37-73% (assuming the reduction is taken equally from both ends). Given the 4 second casting time of Utsusemi: Ichi without haste that buffed interruption rate down would give a player a window of only 1.44 seconds in which to be interrupted. Stack up even more Spell Interruption Rate %- bonuses and your casting window grows even larger to deal with fast-attacking mobs; and assuming the previous modifiers of casting skill, damage, and mob difficulty as part of the model too.


Thoughts, questions, comments? Wall-o-Text? Banished to Zam?

[Plow]

I believe you can be hit before exactly 15% and/or after exactly 85% casting and have no chance for interruptions.

You've got to remember though that the casting gauge you see is not accurate at all.

Oh and it's definately not purely that, you can be hit by things right in the middle and still cast right through it.

[Goddess]

Goddess starts casting Dia on the IT Monster.
The IT Monster hits Goddess for 2 points of damage.
Dice Roll! The hit rolls 679!
Goddess' casting is inturrupted.
Goddess starts casting Dia on the IT Monster.
The IT Monster hits Goddess for 242 points of damage.
Dice Roll! The hit rolls 512!
Goddess casts Dia.
The IT Monster takes 2 points of damage.

[miokomioko]

Perhaps it is just as simple as getting hit any time during the actual casting = chance of interruption. The inconsistancy being from the lag and delay and overall inaccuracy of the casting time bar we see move across, therefor what we visually see is pretty much never the actual casting time.

P.S. I wish monsters and players had the same spell interruption calculations. Pretty much bullshit that a lv.20 monster can interrupt a lv.75 player with a 10 dmg hit but not vice versa.

[Suiram]

I'm pretty sure that if a mob hits you with a hit that would interrupt casting but stoneskin absorbs it and it does 0 damage, it won't interrupt, but if it absorbs all of stoneskin and does at least 1 damage than it will interrupt with the % likelyhood that it would have, had it done the full damage without stoneskin. For example, 350 stoneskin, a hit for 349 will never interrupt, but a hit for 351 will interrupt with the same % chance that it would have, had you not had stoneskin on at all.

As for casting %, your spells fire well before 100%, it's around 75%, but taking into account the time it takes for your client to communicate with the server it could be something like 65% or 70%. I'm pretty sure that the delay in communication is also what accounts for spells not being interrupted below a certain %. For example, it hits you at 25%, but doesn't interrupt, it could be because it took 15% for the "start casting" message to get sent to and processed by the server, and 15% for for the "enemy is hitting you" message to be sent to and processed by your client, so in reality it hit you before you even started to cast. A good way to see if this is really the case would be to start a long cast-time spell like ancient magic and get hit around 20% or so, and see if it won't still get interrupted (I'm wagering it would).

[Kaylia]

Server ping
When you get hit before x% and it doesnt interupt, it's because your information hasnt reach the server. There is 200-300 ping (0.2-0.3sec) between Japan and USA, and it's basically the delay you have to start casting

Example:
You start casting at time 0.0
Server receives your spell casting at 0.3sec, but it sent monster's action at time 0.2999.
You receive monster's action 0.5999sec after you start casting, but on the server, you never got hit during the casting.

It's also true for the end of the spell, where you can get hit while you are still casting, but it's done on the server already. However, spell do finish before 100%, ping or not, so once the spell is out, you cant be interupted anymore.




Interupt

What we know:
- No matter what the damage are (1 or 300), higher level monsters will have a much higher chance to interupt you than low level monster.
- Your spell skill increase your chance to not be interupted.


When there is a player vs enemy situation in FFXI, there is almost always a "stats" vs "opposite" stats formula. Level vs magic skill level doesn't work really well, even if it's not impossible. It's probably something more basic like "weapon skill vs magic skill" (269sword skill vs 290 elemental magic)

Even match seem to give an interupt rate around 50% when you are A+ in a skill.


-Crit seem to influence chance of interupt (could just be dmg tho).
-Probably like evasion, but chance of being interupt seem to cap around 95%

[genome]

Things like bell curves are more realistic in real life.
In FFXI, there would be no reason to add some fake statistical model around the exact casting time to calculate interruption rate outcomes, especially in the interest of speed the most likely implementation is probably something like a uniform cutoff shape, which you implement with a couple of simple if statements, for example something like:

IF (30 < casting time < 70) IF ( f(damage, -%interrupt, randomRoll, otherstuff)>.5) [Interrupt]

Then the way the -%interrupt is implemented is probably as a weight in the random roll, with no interrupt gear any roll over 500, say 600, would interrupt, with -25% interrupt a roll of 600 would not interrupt.

The devil is in the details though, and testing interrupt rates effects would be very difficult (you would need statistics there, in the -analysis- of all those random trials, but the distribution across casting times between 30 and 70 should be uniform). Plus there's going to be a cap imposed on interrupt gear and aquaveil, which will also be hard to guess just from trying to get interrupted tons of times.

EDIT: Kaylia the server ping and lag are definitely factors in apparent inconsistencies and a few flukes where it might seem you get interrupted even before ~30 or after ~70% (or whatever those exact numbers are), but it's definitely not what creates those "safe" regions. You can try it for extremely long spells with different casting times, teleport, reraise, and songs... You can cast up to around 70% and then start moving, and for those spells they still have a few seconds before finishing, and it will still go off at the end.

[Alastaire]

I've experienced some VERY strange instances in the past, where if I've been goblin rushed while casting Utsusemi: Ichi, knocked back, ran back to where I started casting just as the spell was about to finish, and it went off. This seems to happen consistently, and a friend of mine who plays BRD says that he noticed he can start casting a song, run around, and as long as he makes it back to where he started casting before the spell finishes, it still goes off.

I'm not sure if this is some kind of glitch, or what.

[izembo]

the game checks if you moved while casting a spell by checking if your at the same spot at start/finish instead of actually checking if you moved, it's kinda a halfassed way to do it but hey, this is SE after all.

Also I think the spell interruption thing is based on mob difficulty, nothing to do with the damage it hits you for. I've had a mob hit on stoneskin and it will always go off, but then when an IT mobs hits with stoneskin on and goes through and does 1 extra damage, most times the spell gets interrupted, whereas when a too weak hits, it barely gets interrupted ever.

[Elmer the Pointy]

What I'm seeking to understand is the range in which one is still able to get hit during the casting period. I've observed that from roughly 0-30% and 80-100% of the casting period I can take a full-strength hit and still have my ninjitsu go off.

You are exactly right. I obtained a few JP guidebooks while working over there and one of them has a little diagram/chart thingy. You are "safe" during the beginning and ending of your casting period.

I hate to be one of those suspense people, but I'm literally running out the door so I will post the picture later

[Phantomwarrior]

iv had the same thing happen with moves like goblin rush while casting ichi.
However, I've had some bazaar things interupt my castings.
While on blm, I would occasionaly get interupted just from gear swap macros. I havn't heard of many other ppl have this happened, but my char would actually move to the side from just a gear swap and interupt castings. One of the most bazaar things I have seen

[Belkin]

Given the 4 second casting time of Utsusemi: Ichi without haste

Haste wont make you cast it any faster, just recast time. Fast Cast onry

[NynJa]

iv had the same thing happen with moves like goblin rush while casting ichi.
However, I've had some bazaar things interupt my castings.
While on blm, I would occasionaly get interupted just from gear swap macros. I havn't heard of many other ppl have this happened, but my char would actually move to the side from just a gear swap and interupt castings. One of the most bazaar things I have seen

ITS SPELLED BIZZARE YOU 11 YEAR OLD ILLITERATE FUCK.

BAZAAR IS WHAT YOU DO TO SELL STUFF WHEN YOURE AFK, BIZZARE IS A SYNONYM OF WEIRD. THEY DONT EVEN SOUND THE SAME, YOU DUMB FUCK.



jesus christ, how do ppl make such absurd typo's that I cant qualify them as typos ??

[Stilgar]

iv had the same thing happen with moves like goblin rush while casting ichi.
However, I've had some bazaar things interupt my castings.
While on blm, I would occasionaly get interupted just from gear swap macros. I havn't heard of many other ppl have this happened, but my char would actually move to the side from just a gear swap and interupt castings. One of the most bazaar things I have seen

This happens alot if you're standing on a slope or other strange surface while you cast, like the vines in the the Shrine of Ru'Avitau. When you blink out and back during an equip swap, you sometimes get put off the abnormal surface, or moved a step or two away from where you blinked out.

[inafume]

Spell Interruption rate is also affected by your Ninjutsu skill (obviously for only ninja spells).

As a level 40 NIN in Riverne A fighting T drakes (with capped Ninjutsu) I've cast through hits plenty of times. But as a 75 THF/NIN fight EPs or even TW I can be interrupted pretty easily.

[Vistani]

iv had the same thing happen with moves like goblin rush while casting ichi.
However, I've had some bazaar things interupt my castings.
While on blm, I would occasionaly get interupted just from gear swap macros. I havn't heard of many other ppl have this happened, but my char would actually move to the side from just a gear swap and interupt castings. One of the most bazaar things I have seen

ITS SPELLED BIZZARE YOU 11 YEAR OLD ILLITERATE FUCK.

BAZAAR IS WHAT YOU DO TO SELL STUFF WHEN YOURE AFK, BIZZARE IS A SYNONYM OF WEIRD. THEY DONT EVEN SOUND THE SAME, YOU DUMB FUCK.



jesus christ, how do ppl make such absurd typo's that I cant qualify them as typos ??

It's bizarre actually lol

[Shuemue]

iv had the same thing happen with moves like goblin rush while casting ichi.
However, I've had some bazaar things interupt my castings.
While on blm, I would occasionaly get interupted just from gear swap macros. I havn't heard of many other ppl have this happened, but my char would actually move to the side from just a gear swap and interupt castings. One of the most bazaar things I have seen

ITS SPELLED BIZZARE YOU 11 YEAR OLD ILLITERATE FUCK.

BAZAAR IS WHAT YOU DO TO SELL STUFF WHEN YOURE AFK, BIZZARE IS A SYNONYM OF WEIRD. THEY DONT EVEN SOUND THE SAME, YOU DUMB FUCK.



jesus christ, how do ppl make such absurd typo's that I cant qualify them as typos ??

jesus christ, how do people feel when they try to correct someone and they're wrong themselves?

http://www.answers.com/bizarre&r=67

[Cheeks™]

For all you career PLDs out there...
Have you noticed at all if blocking an attack with your shield will increase your chance for getting the spell off?
I rarely get hit on BST, and if I'm lolmeleeWHMing I sub /nin for dual-wield anyways - So I don't really know. And I can't test it well myself because of a gimpy Shield skill and I will get 2 shotted by anything significant.

[Asherek]

ITS SPELLED BIZZARE YOU 11 YEAR OLD ILLITERATE FUCK.

BAZAAR IS WHAT YOU DO TO SELL STUFF WHEN YOURE AFK, BIZZARE IS A SYNONYM OF WEIRD. THEY DONT EVEN SOUND THE SAME, YOU DUMB FUCK.



jesus christ, how do ppl make such absurd typo's that I cant qualify them as typos ??

http://dictionary.reference.com/browse/bizarre

“Uh-oh! Sounds like somebody's got a case of the Mondays!"

For all you career PLDs out there...
Have you noticed at all if blocking an attack with your shield will increase your chance for getting the spell off?
I rarely get hit on BST, and if I'm lolmeleeWHMing I sub /nin for dual-wield anyways - So I don't really know. And I can't test it well myself because of a gimpy Shield skill and I will get 2 shotted by anything significant.

Actually, if anything since S/E changed Shield Block the first time, I've noticed I'm more likely to get interrupted while casting a spell if I shield-block while casting it instead of getting hit, although it's probably a placebo / bad observation on my part.

[inafume]

For all you career PLDs out there...
Have you noticed at all if blocking an attack with your shield will increase your chance for getting the spell off?
I rarely get hit on BST, and if I'm lolmeleeWHMing I sub /nin for dual-wield anyways - So I don't really know. And I can't test it well myself because of a gimpy Shield skill and I will get 2 shotted by anything significant.

Actually, if anything since S/E changed Shield Block the first time, I've noticed I'm more likely to get interrupted while casting a spell if I shield-block while casting it instead of getting hit, although it's probably a placebo / bad observation on my part.

That's because prior to the shield change, all damage was negated from a shield block. You didn't get hit, therefore can't get interrupted.