Elemental and Bonus weapon damage
From this Darkpaw forum post by niente, EQ Developer.
Elemental damage works like so:
 Accumulate all the elemental damage on a weapon and its augments.
 For each resist type, if the NPC has 200 or less of that resist, do a roll
 Roll from 0 to 200
 Subtract the NPCs resist of that element type from the roll
 If the remaining value is less than 100
 Multiply the elemental damage by our remaining roll and divide by 100 (integer division)
 Otherwise add 0 damage
Short example  a weapon has 10 fire damage and an NPC with 100 fire resist.
If we roll 150, subtract 100 FR, our result is 50, we multiply our damage by 50 / 100 and get 5 bonus fire damage on the swing.
There are a few interesting things to draw from this which should probably be updated:
 If we have only 1 elemental damage, our max roll is 99/100 of the value and 99 / 100 (int) is 0 so it does nothing.
 We do these rolls for each swing of a weapon if they have that type of elemental damage (i.e. if you have a weapon that does fire damage and an aug with cold damage it will roll twice for every swing).
I considered adding damage bonus to the ratio when working on this previously but didn't because the damage bonus would add a type of invisible complexity and it's also fairly static for players. Here is the damage bonus equation which I think players have figured out already probably:
 If you are at least level 28
 If you are using a 1H your modifier is 0.8, if you are using a 2H it is 1.1
 If your PC level (PCLevel) is greater than the damage on the weapon (WepDamage), use PCLevel, otherwise use WepDamage
 Multiply the 1H/2H modifier from step 2 by PCLevel or WepDamage from step 3, multiply that by:
 Divide weapon delay (capped at 50) by 40.0
 Multiply by PCLevel divided by 100.0
Since I didn't write that out very well here is the equation:
Damage Bonus = 1H/2H mod * (PCLevel or WepDamage) * WepDelay / 40.0 * PCLevel / 100.0
As an example here's my 115 rogue using the 2.0:
Damage Bonus = 0.8 (1H modifier) * 115 (PCLevel) * 19(Delay) / 40.0 * 115 (Level) / 100.0 = 50.255 ~= 50
Your damage bonus in the item display window is used in combat as your "minimum weapon damage" and a handful of other things are added to it after the fact. I think it's easiest to think of it as, actually, a damage bonus applied to each hit.
Edit: A player corrected me on a mistake with the elemental damage roll; if NPC resist is very low we don't do a roll at all and the full elemental damage is used. Sorry for the mistake!
