iRO Wiki Classic's definition and calculation for DEF
See DEF for more detail.
Defense: Your defense rating against physical damage. It is shown as A + B in the stat window, where A is item-based DEF rate, and B is VIT-based DEF rate. The item-based DEF rate cuts damage by %, whereas VIT-based DEF rate is pure reduction with that number. Be aware that the status window does not accurately represent the DEF added by upgraded items. Each + on an upgraded item is shown in the status window as 1 item-based DEF, however damage is calculated with each + providing only 70% of 1 DEF (so 0.7 DEF). This means, if you have DEF listed as 10+5 and enemy just did initial damage worth 80, then you'll receive 67 damage.
Defense is split into two parts - Hard DEF and Soft DEF.
Hard DEF is the variable that you'd get from your Armors and its upgrade level. For every upgrade on your armor, it gives a bonus +1 DEF on your Hard DEF. And Soft DEF is basically your VitDEF (base and bonus). Your Hard DEF is the number on the left side of the summation of your defense, Soft DEF is the number on the right.
What's the difference?
- Hard DEF is a % damage reduction from Physical attacks giving 0.8-0.9% reduction for every 1 DEF, and Soft DEF is a basically a flat damage reduction. Let's say I have a defense of 40+127, and my opponent has an ATK value of 1500. Considering that I'm not wearing any damage reduction equipment (aside from my armor def), and my opponent does not use any damage boosting equipment, the calculation for the total damage done to me with a melee attack would be:
Total Damage Reduction=(Enemy ATK - ((EnemyATK*HardDEFper) + 127)) = 833
It is a huge damage reduction, but on this server's standards, it is hard to get such Hard DEF values without sacrificing Armor cards, and add the fact that you are prone to being a killed by any item that is designed to turn your DEF against you, such at Thanatos Card and Ice Pick.
What if I have a negative HardDEF value?
- In a very condensed version, you basically take additional damage depending on your HardDEF, plus your SoftDEF value.
HardDEF = -27
SoftDEF = 124
EnemyATK = 1500
TotalDamageReceived = 1500 - ((1500*(-0.24))+124)) = 1736
How does Thanatos Card and Ice Pick work?
Their script's main function is bDefRatioAtkRace. Since Matias won't let me see the actual formula for the function, I've done quite a bit of research and found out its formula (on official servers) is (ATK*((HardDEF+SoftDEF)/100)). Though I've heard before that Maurice actually tweaked that ratio.
Going back to the previous calculation, if my opponent is using an Icepick (ATK:80), and he hits me with Melee damage, the new calculation for it will be:
HardDEFval = 40
SoftDEFval = 127
EnemyTotalATK = ATK = 1580
TotalDamage = (1580*((40+127)/100)) = 2,639
I have not completed the part of research where if the damage output, post Thana/Icepick calculation, will still be reduced by the %reduction from HardDEF. But theoretically, IF HardDEF and SoftDEF still reduce the total damage, then the damage output will be around 1,562.