Earthquake spell math not adding up - trying to make sense of it

[0jij0]

That spell is useless
totally useless

[Mahonroy]

If it does a percentual based damage ON THE REMAINING HITPOINTS! Then an earthquake spell can never take out a building! Because a percentage is never the full value except for 100%! For example if you have a building with only 100 Hitpoints remaining and even if the earthquake spell would do 99% damage then the building would still have 1 hitpoint.... So can somebody explain me why earthquake spells can take out buildingS? Maybe I am just dumb in maths! Thanks

This was explained in the original post:

Now lets talk about the threshold at which the building collapses. In the earthquake spell description it mentions that buildings with low health will suddenly collapse. The reason for this is that if you only rely on a spell taking away a percentage, it will never reach 0 ever (its an asymptote), so there must be a threshold of some sort.

[Ospite]

This was explained in the original post:

If it does a percentage based damage on the remaining Hitpoints it can never reach 0 Hitpoints so it can't take out buildings! Even if it has 1 Hitpoint and we would do a 99 % damage then the building would still not reach O Hitpoints! The earthquake spell is not well explained by SC or maybe it's just me that can't find the exact description of earthquake spell! But Maths is Maths and the explanation is above....

[Yoyobuae]

If it does a percentage based damage on the remaining Hitpoints it can never reach 0 Hitpoints so it can't take out buildings! Even if it has 1 Hitpoint and we would do a 99 % damage then the building would still not reach O Hitpoints! The earthquake spell is not well explained by SC or maybe it's just me that can't find the exact description of earthquake spell! But Maths is Maths and the explanation is above....

In game description:

Weaken walls and buildings with crippling earthquakes!

Earthquake Spells cause structures to lose a portion of their remaining hitpoints. Walls are specially vulnerable to this effect. Earthquake Spells can also cause structures that are almost destroyed to collapse instantly!

[lrbs1980]

If it does a percentage based damage on the remaining Hitpoints it can never reach 0 Hitpoints so it can't take out buildings! Even if it has 1 Hitpoint and we would do a 99 % damage then the building would still not reach O Hitpoints! The earthquake spell is not well explained by SC or maybe it's just me that can't find the exact description of earthquake spell! But Maths is Maths and the explanation is above....

Maybe the explanation is somewhere in the last part of your first post on this thread...

[KletusfromEvilQueso]

Im still interested in seeing higher level earthquake spells in action. It has to improve somehow so I assume it must be to lower inferno hp or kill walls with less than spells.

[KJ]

Imagine hitting only the Townhall with all Eq spells will never get you even 1 star? hehe

[Mahonroy]

It's neither. Each EQ spell actually consists of three hits. And for walls the damage of each hit is multiplied by four. For level 4 EQ spell:
Damage of spell = 12%
Damage of hit = 4.1% (because (100% - 4.1%)^3 = 88%)
Damage of hit against wall = 16.4%
Damage of spell against wall = 42% (because (100% - 16.4%)^3 = 58%)
Damage of three spells against wall = 80% (actually slightly over 80%)

The fourth spell then immediately destroys the wall (with the first hit), because the wall is slightly under 20% HP.

Not sure if it is a bug or intended, but level 1 EQ spell gets added the same bonus % damage against walls as the level 4 spell does.

So level 4 spell gets added damage (per hit):
16.4% - 4.1% = 12.3%

And for some reason level 1 spell gets added the same damage increase (per hit):
2.1% + 12.3% = 14.4%

Thus one level 1 spell actually does:
(100% - 14.4%)^3 = 63% (meaning 37% damage)

Then doing the math for four level 1 spells:
0 spells = 100%
1 spell =63%
2 spells = 40%
3 spells = 25%
4 spells = 16%
(hmm, your observed numbers are around 10% higher than my calculations, maybe the HP bar has an offset of sorts?)

On that last spell the first two hits actually lower the HP down to 21% and then 18%, and it is the very last hit the one which destroys the wall (because HP is under 20%). This also observable in replays (just drop spells one by one, making sure to hit a collector as well to count the hits as they happen).

Thanks for the explanation! Let me see if this adds up...
So I will do your calculations for the lvl1 spell:
(1 - x)^3 = 0.94
x = 0.020414
Damage of hit = 2.041%
Damage of hit against wall = 8.166% (from 2.041 * 4)
(1 - 0.08166)^3 = 0.77448
Damage of spell against wall = 22.552%

How are you calculating the remaining percent after each spell using the 22.552%? I am curious how you got your 1 spell = 63%, 2 spells = 40%, etc. Thanks again!

[Yoyobuae]

Thanks for the explanation! Let me see if this adds up...
So I will do your calculations for the lvl1 spell:
(1 - x)^3 = 0.94
x = 0.020414
Damage of hit = 2.041%
Damage of hit against wall = 8.166% (from 2.041 * 4)
(1 - 0.08166)^3 = 0.77448
Damage of spell against wall = 22.552%

How are you calculating the remaining percent after each spell using the 22.552%? I am curious how you got your 1 spell = 63%, 2 spells = 40%, etc. Thanks again!

The damage increase against walls for level 1, 2 and 3 earthquake spells is higher than just 4x. Each hit gets an added 12.1% damage added (the same % damage increase level 4 spell gets).

So redoing above calculation:
(1 - x)^3 = 0.94
x = 0.020414
Damage of hit = 2.041%
Damage of hit against wall = 14.141% (from 2.041 + 12.1)
(1 - 0.14141)^3 = 0.63293
Damage of spell against wall = 36.707%

I not sure why SC did the calculation like that (might even be a bug), but it just fits perfectly with my in-game observations. It also fits perfectly with 20% as the threshold for walls collapsing when hit by earthquake.

If that turns out to be a bug and it gets fixed, then I would expect it to take 7 level 1 earthquake spells to destroy a wall.

[RockyJoeHawkins]

If a wall has 1000 health and the EQ does (6%x4) that's 24% so now it's at 760, next one does 24% of 760 not of the original 1000.

That's my understanding anyways.

And if not that on walls it is on buildings at6,8,10,12% w.e.