How are rod/spell accuracy calculated?

[Gorgondantess]

Recently, I was playing a Pakellas worshipper, and descended the Lair with my mental checklist of enemies I'd have to prepare for: Hydras, Elephant Swarms, Hydras, Spiny Frogs/Black Mambas, Hydras, you get the idea. I found myself woefully unprepared for most of them save my recent god gift Rod of Inaccuracy, but descended anyways - and when I entered the Lair, I found it didn't live up to its name. It wasn't inaccurate at all! I never missed a hydra once, though that's to be expected. But it worked against Spiny Frogs, even. And then I used it on a swarm of nagas outside the snake pits and cut down four of them in three casts. And then I ran into a Black Mamba and, hey, why not? Got a solid 50% hit rate against it! In fact, I daresay it was more accurate than my previous Pakellas worshipper's Wand of Lightning, which made no sense at all - until I realized I was wearing a randart ring of +9 Dex with this character, and it started to make more sense. I still wasn't sure, though, I browsed the wiki for information, but it was vague and outdated as always, so I ask you:

tl;dr: How exactly are rod attack's accuracy calculated? Is it Dex? Level? Evocations? Static? A mix of some? Was it the ring, or should I let this string of luck ride and roll a Chaos Knight next time? Also, what about spells? And is there a good resource for finding this information other than wasting you good peoples' time?

(Also, on the topic of Dexterity, I understand that they removed Dexterity's impact on damage for melee weapons, but what about UC? And sorry if all of this is in the wrong board, btw.)

[genericpseudonym]

For normal spells, accuracy is based only on spellpower (which can be increased by casting skills, int, relevant elemental staves/rings, etc.)
For rods, accuracy still comes from spellpower, but the spellpower is based only on evocations.

However, the rod of inaccuracy doesn't do either of those things. It always has exactly 1 accuracy (unless the target is affected by halo/corona, which gives +1d10 to hit), so it can only hit enemies who roll a 1 on their EV roll. It will still always hit enemies who are asleep/paralysed, and enemies who haven't noticed you yet get their EV halved.

Dex doesn't affect damage for normal Unarmed, but it does help if you have the Blade Hands transmutation active.

[Gorgondantess]

For normal spells, accuracy is based only on spellpower (which can be increased by casting skills, int, relevant elemental staves/rings, etc.)
For rods, accuracy still comes from spellpower, but the spellpower is based only on evocations.


However, the rod of inaccuracy doesn't do either of those things. It always has exactly 1 accuracy (unless the target is affected by halo/corona, which gives +1d10 to hit), so it can only hit enemies who roll a 1 on their EV roll. It will still always hit enemies who are asleep/paralysed, and enemies who haven't noticed you yet get their EV halved.


Dex doesn't affect damage for normal Unarmed, but it does help if you have the Blade Hands transmutation active.

Very interesting! Thank you very much. That seems really, really low, though... unless my numbers for evasion/to-hit calculation are off. Could anyone possibly enlighten me to how it's calculated to begin with? (And, once again, being pointed to a reliable source for finding that information on my own would be much appreciated!)

(Speaking of which, I just picked up a Rod of Inaccuracy on DL2 with a new character. TSO?)

EDIT: I also just remembered that I was wearing a ring of slaying +5. I know that hasn't been a thing for anything but melee/ranged attacks for a long time, but could a recent patch have changed that? The reliability I had with that rod is starting to baffle me...

[duvessa]

fedhas instead of tso, you get the same accuracy bonus and fedhas is actually useful

[genericpseudonym]

It's worth pointing out that most monsters have much lower AC/EV than players do, which is why player ghosts are often so tanky.

Hydras, for example, have 5 EV, Black Mambas have 15, and Orbs of Fire have 20 (as well as 20 AC).

As for where to get this info: The wiki is okay but it's often inaccurate or out-of-date. If you want accurate info you should probably ask the crawl IRC, query the knowledge bots inside that IRC, or just go code diving.

[Sandman25]

As far as I remember primary reason is that unlike player EV monster EV is rolled twice vs bolt attacks.
So if monster has EV 10, first you roll X=d10 and then you roll dX and then compare it with player d{to_hit}.

[duvessa]

As far as I remember primary reason is that unlike player EV monster EV is rolled twice vs bolt attacks.

No, player EV is "rolled twice" too.

[Sandman25]

Really?
I still see the comment in https://github.com/crawl/crawl/blob/mas ... m.cc#L5007
The comment sounds like player has advantage over monsters.

[duvessa]

I'm an idiot, you're right.

[Sprucery]

As far as I remember primary reason is that unlike player EV monster EV is rolled twice vs bolt attacks.
So if monster has EV 10, first you roll X=d10 and then you roll dX and then compare it with player d{to_hit}.

Oh, I was thinking that I've felt like a rod of inaccuracy hits a shadow dragon more often than 10% of the time. This explains it.