Simulation: Partial Resists

by Tachyon on Sun. 13. June 2010, 03:13

Filed under: dps, simulation, theorycrafting, fire, resists

The development of the new DPS-simulation engine is progressing as planned, and requires more and more time doing research of the spell mechanics, to find out how the spell effects work in detail. It's very hard to find any fundamental information on that topic, so I had to switch back to experimental mode and find it out myself.

One particular question I wanted to have aswered today:

How much of a spell is partially resisted (absorbed) by boss targets?
Bosses have a built in resistence mechanic that lets them absorb a part of the damage. The common knowledge is that bosses count as maxlvl+3 mobs (in the WotLK version: level 83), and that they gain 5 resistence per additional level (15 overall). But I have noticed before that the resists fluctuate, sometimes more is resisted, sometimes less, and in some cases nothing is resisted at all.

Partial Resists

To test the partial resists, I unequipped any items that have a +Spelldamage proc, and casted Arcane Missiles on a Heroic Training Dummy. To record the data, I used Fraps and viewed the video in slow motion to note down the damage and absorbs for each tick.
Here's an excerpt of the collected data (in brackets: partial resists)

1099 (275), 2147 (275), 2446 (137), 1374, 1236 (137), 1374, 1236 (137), 2684, 1374, 2147 (275), 1236 (137), 1099 (275), 2415 (137) ...

The resists were either 0, 137 or 275. In relation to the damage before resists, this was exactly 0%, 10% and 20%. The spell crit modifier for Arcane Missiles (with CSD and the AM Glyph) is 1.95375, and the critical spell hits show that the resistance happens before the crit factor is applied.

Now I needed more samples to quantify how many spells have 0%, 10% and 20% resists. For that I parsed the combat log from our raid tonight with a total of 487 samples on 3 bosses. Result:

257x 0% resist (~ 1/2)
152x 10% resist (~ 1/3)
87x 20% resist (~ 1/6)

I have yet to verify these observations with other spells, but I assume for now that all spells are affected the same by partial resists.

EDIT 2010-06-14: Interesting side note
Ingite is affected by partial resists as well. Critical fire spells get thus taxed twice (once for the spell, once for the ignite DoT). This effect is known as Double Dipping.

7 Comments

U1z wrote:

posted on Mon. 14. June 2010, 14:38

Very interesting, this is something I wondered about myself as well!

Your conclusions beg another question though, is it worth gemming a bit of spell-pen for pve?

Tachyon wrote:

posted on Mon. 14. June 2010, 16:25

Good question! Spell penetration was a superb stat back in vanilla WoW when bosses had resistances against specific elemental magic damage.
The 'common knowledge' is that spell penetration is useless against bosses, but I'll try to test tonight if it really has no effect.
(If you want to test it yourself: Equip some gear with spellpen. gems, and test on a heroic target dummy. Note down any partial resists, check whether they still follow the 0%/10%/20% absorb pattern, and how the distribution looks like).

Tachyon wrote:

posted on Mon. 14. June 2010, 22:45

I repeated the test with 60 Spell Penetration, and had the same results as without.
Spell Penetration thus had no effect at all on the partial resists of bosses.

U1z wrote:

posted on Sun. 20. June 2010, 21:51

Thanks a lot for testing Tachyon!
You truly are my primary source of advanced mage math.

Gotxi wrote:

posted on Wed. 23. June 2010, 10:46

For me too!

I talked with a friend about partial resist some weeks ago, he uses a shadow priest. He told me he was confused because is hit-capped and even with that, bosses resisted some of the damage he deals. I was not aware of that because i dont use scrolling combat text and i don't have such info.

So i hope you can explain us some of the mistery

Gotxi wrote:

posted on Wed. 23. June 2010, 10:50

Sorry for double posting. I was searching in wowwiki and only found this:

"Partial resists only reduce the damage received by a percentage; these can only occur with non-binary spells"

What means "only occur with non-binary spells"?

Tachyon wrote:

posted on Wed. 23. June 2010, 11:53

Hi Gotxi,
Frostbolt used to be such a binary spell (as it has a Damage and Snare component). As the snare component isn't affected by the absorb, neither the damage component was, so there were no aborbs for Frostbolt (this was in fact a hidden damage boost for Frostbolt and part of the reason Frost was a viable raiding spec, as all other schools were affected by a 6.6% damage loss due to absorbs).

This was fixed in patch 3.0 (the WotLK attunement patch); Frostbolt is now also affected by absorbs, and never got any compensation for the damage loss, causing Frost raiding specs to fall even further behind Fire and Arcane.