AC vs. EV

[Francis]

Okay, I've been playing Crawl for a while. Like, over a year, so maybe I should be embarrassed that I don't know this yet. . .
but I still don't fully understand the distinction between AC and EV.
What's a simple way to determine how much any given piece of armor will help me?
What's the difference between AC and EV and what factors should I be taking into account(other than racial aptitude) when choosing between light armor, heavy armor, or a robe?

[KoboldLord]

Okay, I've been playing Crawl for a while. Like, over a year, so maybe I should be embarrassed that I don't know this yet. . .
but I still don't fully understand the distinction between AC and EV.
What's a simple way to determine how much any given piece of armor will help me?

The basic idea is fairly simple. Moderate oversimplifications follow:

If you have an AC of 10, every time you get hit the damage is reduced by a number from 0 to 10. If you have an AC of 20, the reduction is from 0 to 20, and so forth. Your average and maximum reductions will be higher if your AC is higher, but you always have a chance to botch your AC roll and have it do nothing.

If you have an EV of 10, you generate a random number between 0 and 10 and compare it to your attacker's hit. If you beat it, you negate the attack, but if you just barely fail you get no reduction in damage. This increases in roughly the same way.

There are complicating factors. In particular, body armor provides Guaranteed Damage Reduction, which basically means that if you botch your AC roll GDR will step in and you'll reduce some damage anyway. Monster hit and monster damage also scale differently at different points of the game.

What's the difference between AC and EV and what factors should I be taking into account(other than racial aptitude) when choosing between light armor, heavy armor, or a robe?

Are you a caster? Then get on a robe, and don't even think about changing until all your spells are at excellent. And even then, just take one step up to leather, and possibly another step up to (swamp/ice/pearl) dragon armor at the very most. Spells are awesome, and you don't want to give them up. Spell success is more important to armor choice than every other factor combined.

If you're not planning to cast, it's fairly safe to go for the heaviest armor you can find if your aptitudes are good. There are other penalties involved, but the extra defense is quite valuable.

[Francis]

Thanks, that's very helpful.
So, I can say that for my current Merfolk Crusader, it's a good idea to wear robes because I'll rely on spells so much.
I was pretty sure that spellcasting was an important factor, and it's nice to have things clarified.

But say I'm playing a character without casting, but with a low armor aptitude - such as a Merfolk Gladiator. Is it a good idea to immediately start wearing heavy armor, even with the low armor aptitude?

[sigfried von murdock]

Not necessarily.

heavy armor will weigh you down and penalize you evasion and accuracy. The AC may be worth it, but you will have a lot more trouble simply hitting a giant bat, or snake. If you rely on mobility or range, than heavy armor earlier on may not be worth it.

Ever run into an ogre really early on? And you ran the heck away because you didn't have the fire power to mess with it?

Well A heavy set of platemail on a level 3 merfolk gladiator who has maybe 1-2 in armour will give you super slug speed. You may have defense, but if you have to run almost anything could outrace you and get a few opportunity attacks, and the probability of you hitting them will take a hit just like your speed. Also the bigger the armor the longer it takes to take off and put on, spending 7 turns to remove cumbersome armour might even make you a bigger target.

Early on high AC can be great, you just have to make sure you are in fight mode far more often than flight mode.

Still despite the penalties of armour and shields, even to skills that they get in the way of like unarmed or magic, they can be useful. Like Koboldlord said: "Spells are awesome, and you don't want to give them up. Spell success is more important to armor choice than every other factor combined." Armour is a no no to casters, and if worn it should be of a light quality, and spell casting and success rate needs to naturally be very high.

Oddly enough I had a Draconian Monk - He used Swamp Dragon armour that he made from a hide and enchanted himself up to +5, and a +3 large shield of protection with additional +3 AC.

Overall my monk at around level 11 naturally had 7 AC and 18 Evasion.
Armour and shield on he had: 23 AC, 10 EV, 31 SH. - This penalized my offensive capabilities, but increased my survivability astronomically since I could evade, then block, then reduce attack damage, and when I was skilled enough in armour and shields and unarmed, my attacks were still strong and accurate. (Very strange character of mine)

Heavy armor early on is gutsy, pros and cons. Biggest concession is accuracy and speed, so the trick is to balance your stats for survivability, if you can move quickly and hit a good deal of the time, but take massive damage on hits, armour might be a bit more important than hitting a bit more often.

[Francis]

Alright, I'm getting a much clearer understanding of what factors I should take into account when choosing what to wear. Thanks for taking the time to type out detailed responses, both KoboldLord and sigfried.
So how can I tell how much a piece of armor will penalize my speed and accuracy?
Also, how should I decide when I should turn armor or dodging training on or off? I can safely assume that it depends on the character, but is there any more specific advice you can offer?
I guess one of the things in Crawl I'm most unsure about is when to turn skills off and when to leave them on, but that's another topic entirely.

Ever run into an ogre really early on? And you ran the heck away because you didn't have the fire power to mess with it?

I certainly have... I've ran away from many an ogre in my time.
And I certainly understand the importance of knowing when to run away in this game.

[KoboldLord]

heavy armor will weigh you down and penalize you evasion and accuracy. The AC may be worth it, but you will have a lot more trouble simply hitting a giant bat, or snake. If you rely on mobility or range, than heavy armor earlier on may not be worth it.

The negative effect to accuracy is relatively minor. Your accuracy penalty will average out as half of your evasion penalty, and unfortunately there are relatively few monsters in the game with decent evasion and most of the few that exist aren't a real threat even if you can't hit them properly. I doubt a non-caster would ever experience accuracy problems unless they happen to run into heavy armor, a large shield, and a heavy weapon all at once in the very early game, since these all have a stacking accuracy penalty that skills eventually partially or fully overcome.

Ever run into an ogre really early on? And you ran the heck away because you didn't have the fire power to mess with it?

Well A heavy set of platemail on a level 3 merfolk gladiator who has maybe 1-2 in armour will give you super slug speed. You may have defense, but if you have to run almost anything could outrace you and get a few opportunity attacks, and the probability of you hitting them will take a hit just like your speed.

Wait, what? Heavy armor doesn't do that in this game.

Pondering does slow you down, but pondering is a specific armor brand that only appears very rarely unless you worship one particular deity. Normal armor with any other brand, or no brand at all, does not affect your movement speed at all. It will not affect your attempt to run away from an ogre.

You may have movement speed mixed up with attack delay.

[sigfried von murdock]

heavy armor will weigh you down and penalize you evasion and accuracy. The AC may be worth it, but you will have a lot more trouble simply hitting a giant bat, or snake. If you rely on mobility or range, than heavy armor earlier on may not be worth it.

The negative effect to accuracy is relatively minor. Your accuracy penalty will average out as half of your evasion penalty, and unfortunately there are relatively few monsters in the game with decent evasion and most of the few that exist aren't a real threat even if you can't hit them properly. I doubt a non-caster would ever experience accuracy problems unless they happen to run into heavy armor, a large shield, and a heavy weapon all at once in the very early game, since these all have a stacking accuracy penalty that skills eventually partially or fully overcome.

Ever run into an ogre really early on? And you ran the heck away because you didn't have the fire power to mess with it?

Well A heavy set of platemail on a level 3 merfolk gladiator who has maybe 1-2 in armour will give you super slug speed. You may have defense, but if you have to run almost anything could outrace you and get a few opportunity attacks, and the probability of you hitting them will take a hit just like your speed.

Wait, what? Heavy armor doesn't do that in this game.

Pondering does slow you down, but pondering is a specific armor brand that only appears very rarely unless you worship one particular deity. Normal armor with any other brand, or no brand at all, does not affect your movement speed at all. It will not affect your attempt to run away from an ogre.

You may have movement speed mixed up with attack delay.

I know attack delay, but I thought speed too. I may be wrong, but I would have to double check.

The accuracy penalty is minor, especially late game, i really just meant early game if you are already have tons of trouble hitting anything.

If applicable I try to get a character well versed in EV, AC, and SH. Maybe I just don't like to be hit = P

[Francis]

Looking at the movement page in the Crawl wiki, it seems like KoboldLord is right - movement speed is something separate from armor that's only affected by things like by spells, potions of speed, mutations, the Ponderousness brand, being overburdened, etc.

[Volgon]

So if my non-caster finds plate mail on level one should I put it on? Or am I better off with chain/ring mail until my armor skill is high enough?

This has always confused me. For non-casters I tend to put on the best AC armor ASAP, and sometimes feel that this a mistake.

[Lawman 0]

This subject is moot since the existence of pearl dragon (or even regular) armor makes having to choose between the two a thing of the past.

[KoboldLord]

So if my non-caster finds plate mail on level one should I put it on? Or am I better off with chain/ring mail until my armor skill is high enough?

This has always confused me. For non-casters I tend to put on the best AC armor ASAP, and sometimes feel that this a mistake.

For the most part, you can go ahead and equip good items. The minor penalties are minor, and Crawl items don't make a habit of trying to kill you for not consulting a spreadsheet.

If your mountain dwarf fighter happens to see some crystal plate mail and an executioner's axe both before the Temple, you might come back and ask again for advice. Aside from that exceedingly rare sort of circumstance, though, you can equip anything you find right away.

[snow]

I'm fairly new to the game and have only won twice but from what I've seen EV is better than AC.

Armor slows your attack speed, lowers spell accuracy, etc. Robes just... help you dodge. Just spamming berserk whenever something is hard isn't going to help when you're fighting a dozen hard enemies at once and the stairs are far away... you're going to want to cast some translocation spells late game and if they keep failing you're going to die.

[vintermann]

My experience with heavy armour is also that it's generally better to go for EV. At best, heavy armour is as good as light, but even then only when you've already ruled out stealth/casting.

I found a Gold Dragon Armour on D:1 once with a merfolk. I wore it out of sheer bloody-mindedness, figuring that -10 EV isn't any worse than 0 EV. He went from disaster to disaster, miraculously surviving until D:8 or so, where he died an ignoble death and left a totally puny ghost.

[LunarHarp]

Slightly off topic but it is good to note that the shield value SH works the same as EV. Shields are a separate check to see if a monster hits you or not. Because of this shields are in fact great for almost all character builds. However, spell casters have to take spell penalties into consideration. Shields with unarmed is not so great since it doesn't go well with being a transmuter (forms can't use shields) and you lose some of the extra attacks (but this is not terrible usually).