Piercing power

[Frightning]

So both types of cannon shells for the tank have a stat called piercing power. What exactly does that do?

[BlakeMW]

Piercing power is related to how many hitpoints the cannon shell can pierce through.

Note that the cannon shell is only allowed to pierce if it kills the target, it will always deal only 200 damage to a target with more than 200 hitpoints, and will not pierce if it does not kill the target. It always deals 200 damage to each target it hits (less if the target has less than 200 hitpoints, but the point is the cannon shell damage is not reduced by having previously piercing)

Against enemies with more than 200hp it will not piece (deals 200 damage)
Against enemies with 200hp it can pierce 1 time and hit a 2nd (400 damage)
Against enemies with 150hp it can pierce 2 times and hit a 3rd (450 damage - 500 if the final target is beefy)
Against enemies with 100hp it can pierce 3 times and hit a 4th (400 damage - 500 if the final target is beefy)
Against enemies with 50hp it can pierce 6 times and hit a 7th (350 damage - 500 if the final target is beefy)

So it appears that each time it kills an enemy its remaining pierce is reduced by the hitpoints of the killed enemy. If remaining pierce is still >= 0 it is allowed to continue on. It is kind of odd that the cannon shell is least effective against big targets.

[Woodmn]

Would be interesting if they added canister rounds to tanks, basically giant shotgun shells that could clear most of a forest or slaughter following biters/ranks of spiters.
http://www.gd-ots.com/LCA_120mm_M1028.html

[Frightning]

Piercing power is related to how many hitpoints the cannon shell can pierce through.

Note that the cannon shell is only allowed to pierce if it kills the target, it will always deal only 200 damage to a target with more than 200 hitpoints, and will not pierce if it does not kill the target. It always deals 200 damage to each target it hits (less if the target has less than 200 hitpoints, but the point is the cannon shell damage is not reduced by having previously piercing)

Against enemies with more than 200hp it will not piece (deals 200 damage)
Against enemies with 200hp it can pierce 1 time and hit a 2nd (400 damage)
Against enemies with 150hp it can pierce 2 times and hit a 3rd (450 damage - 500 if the final target is beefy)
Against enemies with 100hp it can pierce 3 times and hit a 4th (400 damage - 500 if the final target is beefy)
Against enemies with 50hp it can pierce 6 times and hit a 7th (350 damage - 500 if the final target is beefy)

So it appears that each time it kills an enemy its remaining pierce is reduced by the hitpoints of the killed enemy. If remaining pierce is still >= 0 it is allowed to continue on. It is kind of odd that the cannon shell is least effective against big targets.

Ok, I get the gist then, but what about the specifics of the mechanics? The Tank, in 0.12.35-0 with Cannon shells does 150 Physical damage and 50 Explosive damage, and has 300 Piercing power. So is the Piercing power number compared against current hp of target, or max hp? If it pierces, does it get to deal full damage to the next target, if not, how is the remaining damage determined based on what happened to the first target? How are the two types of damage handled for the first target in that case?

[BlakeMW]

It's compared against the current hitpoints, you'll note if you shoot a cannon shell at a spawner, the first cannon shell will be absorbed and not pierce, the second shell will kill the spawner and pierce though.

Basically in order to pierce it has to kill the target, all that matters is the amount of hitpoints the cannon shell removed in practice, that is, post-resists, and all damage types taken together. I haven't tested it, but I imagine if you gave a target negative resists the cannon shell wouldn't pierce through a target with more than 300 hitpoints even if it could 1-shot it as it seems to be the amount of hitpoints actually removed that matters.

One final thing to note: The explosive cannon shell does not explode (inflict AoE damage) when it pierces, only when it is runs out of pierce or range. This means if you fire an explosive cannon shell at a group of low-hp targets like small biters or spitters it can actually punch through a couple of the enemies and fly off into the distance, resulting in only 1 or 2 enemies being killed instead of exploding and killing the whole group. It makes the explosive shell particularly ineffectual against groups of small targets. I generally consider the pierce on the explosive shell more a downside than an advantage.
I believe the explosive cannon shell inflicts both piercing and explosive damage on targets it pierces through (although with only 30 piercing power this wont be noticeable, but if you modded an enemy to have 15 hp and 75% physical resist I'm pretty certain the explosive cannon shell would kill it and pierce through).

[Frightning]

It's compared against the current hitpoints, you'll note if you shoot a cannon shell at a spawner, the first cannon shell will be absorbed and not pierce, the second shell will kill the spawner and pierce though.

Basically in order to pierce it has to kill the target, all that matters is the amount of hitpoints the cannon shell removed in practice, that is, post-resists, and all damage types taken together. I haven't tested it, but I imagine if you gave a target negative resists the cannon shell wouldn't pierce through a target with more than 300 hitpoints even if it could 1-shot it as it seems to be the amount of hitpoints actually removed that matters.

One final thing to note: The explosive cannon shell does not explode (inflict AoE damage) when it pierces, only when it is runs out of pierce or range. This means if you fire an explosive cannon shell at a group of low-hp targets like small biters or spitters it can actually punch through a couple of the enemies and fly off into the distance, resulting in only 1 or 2 enemies being killed instead of exploding and killing the whole group. It makes the explosive shell particularly ineffectual against groups of small targets. I generally consider the pierce on the explosive shell more a downside than an advantage.
I believe the explosive cannon shell inflicts both piercing and explosive damage on targets it pierces through (although with only 30 piercing power this wont be noticeable, but if you modded an enemy to have 15 hp and 75% physical resist I'm pretty certain the explosive cannon shell would kill it and pierce through).

So it IS current hp....interesting. I tested the explosive shells to check my suspicions about how the AoE worked and confirmed I was right: The splash damage is just the 80 Explosive damage part, the 30 Physical damage does not splash. I used a Medium biter as test target, a direct hit killed it: 30-4=26 Phys plus 80*(100%-10%)=72 Exp=dead Medium biter, but hiting a nearby Big biter resulted in a heavily damaged Medium biter (just the 72 Explosive damage after resists versus 75 hp) so it lived. Now I'm wondering if the Explosive damage is applied when the regular cannon shell pierces or not (e.g. ~180 hp target would it pierce?)

[BlakeMW]

The regular cannon shell definitely seems to inflict 200 damage to targets it pierces through. Try shooting steel chests (200 hp) and you'll see it kills two of them, the only way this is possible is if it deals both the physical and explosive damage on piercing as otherwise it could only deal 150 damage on a pierce. This perhaps should be considered a bug. Though I think the whole mechanism deserves to be reworked. I think it'd be better if the cannon shell inflicts maximum say 300 damage and just keeps piercing until it runs out of damage. The fact that it still deals maximum damage regardless of how many targets it has pierced through is pretty odd, does kinetic energy mean nothing?