Advanced Mechanics

Welcome to the advanced game mechanics thread, where I go over some mechanics of the game that you may not know about.

On each link, you can see the build that the post is last updated to. This will help ensure that you have the most accurate information possible!
Current Build: B29 H0
[li]Trivia and One Liners. Build not applicable.[/li]
[li]Probablity to Hit | OA/DA Formula B27 H0[/li]
[li]Various Reduced Target’s Resistance B27 H0[/li]
[li]Weapon Pool System (Chance to Use an Attack) B26 H3[/li]
[li]Armor and Armor Absorption B27 H0[/li]
Currently Being Written Up:[ul]
Currently Being Tested, or on Hold to be Tested:[ul]
[li]Attack Speed[/li]
[li]Conversion on Skills and Items[/li]
[li]Classic Targetting[/li]
[li]Ceno’s 3 things.[/ul][/li]In addition to these links, we also have a few very prominent resources to help you learn more about Grim Dawn:[ul]
[li]Official Grim Dawn Game Guide - Allows you to easily find information on a variety of Grim Dawn mechanics.[/li]
[li]Game Info and Features Sub-Forum - Contains a plethora of information from our very own moderator eisprinzessin about a variety of things.[/li]
[li]Grim Calc - Maintained by Stormcaller in this thread, allows you to make a skill tree build quickly, and share it with a link through a save button.[/li]
[li]Graceful Dusk Item Database - Maintained by Shalie in this thread, allows you to find nearly every item in Grim Dawn.[/li]

Go for it, that’s why I have the linking system on this post, so I can just add another peice to the thread and then link it. This thread is intended for all sorts of anything related to advanced mechanics, including queries, discussions, and corrections. You can of course make your own thread if you want, don’t let me stop you from being you!

As always, thank you for taking your time to read this.

Attachment: PTH and THR.jpg
Attachment: Hit Crit chances.jpg
Attachment: Crit level chances.jpg
Attachment: hitcritcode.txt

1 Like

This post is dedicated to small or basic tid-bits of information that are too short or too simple to garner a whole seperate post for.

[ul][li]The items you occasionally see fade away on the ground are called broken items. 1, 2[/li]
[li]Grim Dawn has a loot filter that you can set in the first page of your options menu. It’s very helpful for keeping the trash out of your eyes![/li]
[li]You can, in fact, zoom the camera in and out. Default keys are mouse up and mouse down.[/li]
[li]Monsters with stars above them are called Heroic Monsters, or Heroes for short. 1[/li]
[li]The only damage multipliers in the game are +n% Damage to <Monster Type> and +n% Crit Damage. Everything else, including +% Total Damage, is additive. New to B27 are a stat found on transmuters called “Damage Modified”, which multiplicatively changes your damage output.[/li]
[li]The only way to reduce Terrain Damage (from Aether Floor and Poison Lakes) is through Damage Absorption on skills like Maiven’s Sphere of Protection.[/li]
[li]For each Skill Point you invest into Mastery, you get 38 Health/Energy and 10 Attribute Points. The different classes divide it up differently.[/li]
[li]The game does not distinguish between Crossbows and Rifles.[/li]
[li]Your character places Salt around Riftgates to stop Aetherials from coming out and slaughtering everyone![/li]
[li]New to B27, each unique source of DoT now does full damage![/li]
Feel free to correct misinformation, suggest additions, or ask questions!

This post is dedicated purely to the Probability to Hit Formula.
B27 H0

Terms Used:[ul][li]PTH = Probability to Hit (NOT “Chance to Hit”/“Chance to be Hit”!)[/li]
[li]OA = Offensive Ability[/li]
[li]DA = Defensive Ability[/li]
[li]CH = Chance to Hit or Chance to be Hit[/li]
[li]CC = Chance to Crit or Chance to be Crit[/li]

PTH = (OA-DA+1275)/15
Due to the rounding of CH and CC in Grim Dawn to the nearest tenth, expect errors no greater than 100.
There exists a relationship between OA and DA, each 15 OA/DA difference between you and the enemy will give 1 more PTH.

Unsimplified Formulas[spoiler]



Example Usage of Formulas:[spoiler]
Lets say we want to find out how much OA this Gunman has. We already know four things:

[ul][li]Our DA: 893[/li]
[li]CH: 91%[/li]
[li]CC: 1%[/li]
[li]PTH: 91 (We know this because CC is less than 10, so PTH = CH)[/ul][/li]We can just plug these numbers into the “OA” formula and we get 983 OA. That’s roughly how much OA the Gunman has.

Lets say we want to find out how much DA Moosilauke, the Chillwind has. We already know four things:

[ul][li]Our OA: 1689[/li]
[li]CH: 100%[/li]
[li]CC: 16.7%[/li]
[li]PTH: 108.04 [Since CC is greater than 10, use the PTH formula][/ul][/li]We can just plug these numbers into the “DA” formula and we get 1343.4 DA. That’s roughly how much DA Moosilauke, the Chillwind has.

Misses, Critical Thresholds, and Weights

This image may make it seem like that PTH and Crits are done by a percentage based system. [b]This is a lie[/b]. Crits, hits, and misses are done via weights. There are always at least 100 weights, and each PTH gives one weight that can hit or crit. There are 6 PTH Thresholds, and a sorta kinda one that I’m just going to call PTH Threshold 0.
PTH Thresholds

[ul][li]PTH Threshold 0: Less than 70 (Less than 1x Damage). X [This color represents a miss for uses later on][/li]
[li]PTH Threshold 1: 70 (1x Damage) X[/li]
[li]PTH Threshold 2: 90 (1.25x Damage) X[/li]
[li]PTH Threshold 3: 110 (1.5x Damage) X[/li]
[li]PTH Threshold 4: 130 (1.75x Damage) X[/li]
[li]PTH Threshold 5: 150 (2x Damage) X[/li]
[li]PTH Threshold 6: 170 (2.5x Damage) X[/ul][/li]
PTH Threshold 0: Less than 70 (Less than 1x Damage).
If your PTH is less than 70, any attacks that land will do (PTH/70)x less damage. So, if your PTH is 65, you will do 92.86% of a normal damage on a hit, or 65/70.

PTH Threshold 1: 70 (1x Damage)
Let us assume you have exactly 70 PTH. This means you have 70 weights that can hit, and 30 weights that can miss. To visualize this, let each “X” be 10 weights:
The game then picks a weight at random, and you will do that amount of damage.

PTH Threshold 2: 90 (1.25x Damage)
So, for values between this threshold (90) and the next threshold (110), you will get a Critical. So, let us assume you have 100 PTH.
Notice that we cannot miss anymore. If our PTH was 99, we’d have 89 Normal Hit weights, and 10 1.25x Crit weights, and 1 miss weight.
Also notice that at PTH=100, you have exactly 10% chance to crit. Pretty nice, eh?

PTH Threshold 3: 110 (1.5x Damage)
So now let us assume that we have 120 PTH. That would lead our weight bar to look like this:
But wait! We have more than 100 weights! That’s right. We have 120 weights in our weight bar (remember that each X represents ten weights). Also notice that we have 90 weights on a normal hit, and 30 (20 1.25x, and 10 1.5x) weights to crit. This means that our Chance to Crit would be CC=1-(90/PTH), or in this case 25%! Let’s keep going!

PTH Threshold 4: 130 (1.75x Damage)
This time let’s assume a PTH of 140:
Our Chance to Crit Formula tells us we have 35.7% Chance to Crit. Not too shabby, eh?

PTH Threshold 5: 150 (2x Damage)
Nothing too special here, let’s just continue what we’ve been doing. Let PTH=160:

PTH Threshold 6: 170 (2.5x Damage)
Let PTH=200:
The only thing to note is that since there is no PTH Threshold above 6, all extra weights are added on as a 2.5x damage multiplier.

So let’s recap, did we notice anything significant?
Well, we noticed that when PTH=100, then CC=10.
We also noticed that at PTH=120, then CC=25.

Well, if you took a guess, you might be able to tell that [b]you can know when you broke a threshold by looking at how much CC you have[/b]. This might not sound like much, but if you know this, then you can know that at CC=47.1%, then you have just barely broken into PTH Threshold 6, and can get those juicy, oh so juicy, 2.5x Crits. Of course you will only have one weight in, so your chance of getting this particular Critical is only 1/170 or .0059% chance.

Here are the CC% and what Threshold you’re in:

CC | PTH Damage Threshold
0.0% | 1 or less
1.0% | 2 PTH 90
18.2%| 3 PTH 110
30.8%| 4 PTH 130
40.0%| 5 PTH 150
47.1%| 6 PTH 170

And that about concludes everything you need to know about the PTH formula. All information is from the Game Guide on PTH Formula. The reason I took the time to write this all down is solely because of Ninetrix and ex_cathedra, who didn’t understand how the formula worked. So you can thank them for their ignorance if this post helped you in some way :smiley:

Special thanks to doublebuck, ex_cathedra, and gabfou for correcting and explaining my errors to me.
A very, very special thank you Grohuf for telling me repeatedly that I have an error. Thanks buddy!

Feel free to correct misinformation, suggest additions, or ask questions!

This post is dedicated purely to the various ways to Reduce a Target’s Resistances.
B27 H0

Terms Used:[ul][li]Absolute = Can be reduced lower than 0%, it is additive.[/li]
Ways to Reduce a Target’s Resistance:
There are three ways to reduce a target’s resistance:[ul][li]n Reduced Target’s Resistance is absolute and cannot be stacked with other unique n Reduced Target’s Resistance debuff sources.* Examples include: War Cry, Plaguebearer’s prefix.[/li]
[li]n% Reduced Target’s Resistance is percentage based and cannot be stacked with other n% Reduced Target’s Resistance debuffs. Although this is percentage based, it can reduce an enemies already negative resistance, further negative. Examples include: Eternal Band, of the Abyss suffix.[/li]
[li]-n% Resistance is absolute. This one is special in that it is part of a debuff as opposed to being a debuff itself. That means that when the general debuff wears out, so does this effect. This can stack with itself. Examples include: Night’s Chill, Curse of Frailty, Olexra’s Flash Freeze.[/li]
*Mark of Dreeg is unique in that if you put a Mark of Dreeg in your 1h weapon, and in your shield or focus, it applies both Mark of Dreeg’s n Reduced Target’s Resistance together.

So, n Reduced Target’s Resistance and -n% Resistance is most effective against any enemies that have a low resistance, as it can bring an enemy’s resistance below 0 meaning that they take multiplicatively more damage.
n% Reduced Target’s Resistance is most effective against any enemy that has a really high resistance, as it will lower the enemy’s resistance the most.

Please note that in ALL CASES for Grim Dawn, flat reductions apply before %reduction, so in our case, the order the resistances would be applied in is thus:[ol][li]n Reduced Target’s Resistance[/li]
[li]n% Reduced Target’s Resistance[/li]
[li]-n% Resistance[/ol][/li]
Note about Reduce All Resist
When a resistance reduces all resists, it reduces Physical, Pierce, Bleeding, Lightning, Cold, Fire, Vitality, Poison&Acid, Chaos, and Aether. It does not reduce CC resistances, like Entrapment, Stun, or Slow.

Reduce all Resist does not stack with Reduce X Resist, only the strongest will apply. For example, if you had 15 reduced resistance and 30 reduced physical resistance, the 15 will apply to all the other resistances while the 30 will apply to the physical.

Example 1:
So, let’s give a complex example:
Let us say we are fighting an enemy with 80% Fire Resistance, and we have: [ul][li]Plague Bearer’s Prefix (lvl 41): “18 Reduced Target’s Resistance for 5 Seconds”[/li]
[li]Olexra’s Flash Freeze (lvl 9): “-46% Fire Resistance”[/li]
[li]of the Abyss Suffix (lvl 46): “30% Reduced Target’s Resistance for 3 Seconds”[/ul][/li]Either the Plague Bearer’s Prefix or Olexra’s Flash Freeze would be applied first, so:
Then the “of the Abyss” Suffix would be applied:

So after all the debuffs, the enemy would have 11.2% Fire Resistance.

Example 2:
Using the same gear and stats from before, let’s do the same example but instead give the enemy 10% Fire Resistance.
Then the “of the Abyss” Suffix would be applied:

So after all the debuffs, the enemy would have -70.2% Fire Resistance.

¹The formula for doing n% Reduced Target’s Resistance to an enemy with negative resistances is slightly different than the one where enemies have positive resistances:
Postive: (Enemy Resist)(1-n% Reduced Target’s Resistance).
Negative: (Enemy Resist)
(1+n% Reduced Target’s Resistance).

A Special Note: Debuffs given through Weapon Damage % will be effected by it, up to 100%. So if you use Phantasmal Blades (30% Weapon Damage) with the “18 Reduced Target’s Resistance for 5 Seconds” from PlagueBearer’s prefix, it will only do 30%*18=6 Reduced Target’s Resistances for 5 Seconds. However, if you do it with, say, Shadow Strike (which gives 330% Weapon Damage at 16/16), it will only do 18 Reduced Target’s Resistance, not of 59.4.

I took a conversation that Ninetrix was having in a Twitch Chat awhile ago to write this. I kept forgetting this information, and that’s why I wrote it. It also happens to help out the various people that come into the forums asking for just this information.
But I seriously wish to attribute all the information here to Ninetrix, without him I wouldn’t know anything about this.

Another thanks to Ninetrix for being so damn knowledgable about the game.

As always, feel free to correct misinformation, suggest additions, or ask questions!

Maybe you could add what happens with resistance if it’s put on negative before % reduction happens. Afaik its multiplied further into negative (like in TQ), but you’d have to test it probably.

Could be that nothing happens, but thought I’d mention it in case my info is right as it could be interesting to put a monster on like -60 flat and then have something like the abyss suffix drop it to -80.

+1 Sticky. Nice write up.

Chance to crit equations are wrong.

Nice thread.

Aren’t those already in the game guide? Same remark for the OA/DA formula.

Readed a bit more. You messed everything about crits.

What do mean, nearly ? :stuck_out_tongue:

Yes, however, not everyone reads the game guide, and there are many newer players that don’t know about the camera or loot options. (See it all the time when I watch first time streamers.)

I, myself, took forever to learn the proper name for heroes, or why items were disappearing.

Additionally, by how thresholds and the formula work, there’s a lot more that can be derived from them. I simply work it all out. Like I said in the conclusion, I wouldn’t have bothered if a few other people understand what Crate wrote in the Game Guide.

What did I do wrong? I verified everything possible in game about them, and went with the game guide on them. It’s not helpful to just say I did something wrong without saying or exaplaining what.

Well, tell me the names and give me the artwork of all the other Legendaries, and other not yet implemented items :wink:

I happen to know that there is exactly one legendary in the Grim Dawn database with stats :slight_smile:

Hm. I think that’s what happens, but I could be wrong. I’ll add it to my list for testing.

Yes, % reductions will further reduce a negative value.

Yes, but is it a flat reduction at that point, or is it reduced by some form of the negative resists of the enemy? That’s the real question.

The PTH equation is correct. Unsure about the OA/DA formulas, will have to extract the latest gamefiles for them.

I can think of a couple that you don’t list…good thing you don’t, either, but I’m pretty sure they’re in the gamefiles. :wink:

Edit: On a totally unrelated note, anyone know what the gamefile is for the 10k-health ring Zantai was using in one of the Misadventures? :stuck_out_tongue: Edit: this thing

On a somewhat related note, is this thread appropriate for asking questions on advanced mechanics (that you haven’t touched on), or would you prefer that in a different thread, Raiyaz?

It’s reduced by the target’s resistance after flat reductions. If an enemy has -50 resistance and then you applied 30% reduced resistance, the target would have -65 resistance.

First you need to simplify formulas. You are writing guide.
PTH = 85 + (OA - DA) / 15
Each 15 OA/DA difference give you 1% PTH

Second, REAL crit chance formula is:
mod = 100 if PTH <= 100
mod = PTH if PTH >= 100
(well, or “int mod = (PTH <= 100) ? 100 : PTH” if you like c++)

crit chance = (PTH - 90) / mod * 100%


They’re just simplified using basic Algebra from the Game Guide
ProbabilityToHit(PTH)=((((Attacker’sOA5)+7500)–( Defender’sDA5))/75)–15

Then verified by having known PTH’s (CH < 100) and getting hit or attacking enemies. Enemies (and players) are given a base OA/DA, and then you have to find their Cunning and Physique amounts. Then you also need to account for Veteran difficulty adding to them. Anddd… you’ll still end up short as there is something else I’m still missing. Doing this will give you the DA for Alkamos of about 1100, while he really has ~1500.

As far as I’m aware, there’s no “OA/DA” formulas, per se.

Technically speaking, I think there are, based on Character Level & Cunning. But I suppose those aren’t the formulas that are relevant to your original post.