After Cast Delay Reduction Algorithm

[Everade]

• rAthena Hash:
  3115a1d

• Client Date:
  2021-01-07aRagexeRE

• Server Mode:
  Renewal

• Description of Issue:

  • Result:
    The After Cast Delay Algorithm doesn't match.
    The skill Poem of Bragi (Magic Strings) after cast delay reduction seems to be multiplicative instead of a total sum of all reductions combined.
    Testing with Kiel-D-01 + Poem of Bragi delivers only a x 0.49 reduction instead of x 0.6.
    The issue could possibly be caused by being calculated similiarly to the Variable Cast time:
    a x ( 1 - b ÷ 100 ) x ( 1 - c ÷ 100 ) = 1470ms
    a = Tarot Card of Fate after cast delay (3000ms)
    b = Poem of Bragi reduction (30)
    c = Kiel-D-01 reduction (30)

  • Expected Result:
    Cast Delay ( seconds ) = BaseDelay × ( 1 − Sum_DelReduc ÷ 100 )
    BaseDelay = Base Cast Delay of a skill.
    Sum_DelReduc = Sum of reductions for Cast Delay.

  Which would result in the expected reduction of:
  a x (( 1 - b ÷ 100 ) + ( 1 - c ÷ 100 )) = 1200ms
  a = Tarot Card of Fate after cast delay (3000ms)
  b = Poem of Bragi reduction (30)
  c = Kiel-D-01 reduction (30)
  In short: calculates first skill based reduction, then gear. Instead of a deduction of the entire sum.

  • How to Reproduce:
    Use both Poem of Bragi (skill) and a Kiel-D-01 Card.
    Then check the after-cast timer of Tarot Card of Fate. (original 3000ms)
    The result will be 1470ms instead of the expected 1200ms.

  • Official Information:
    https://irowiki.org/wiki/Skills#Cast_Delay
    Unfortunately i don't have any KRO source.

• Modifications that may affect results:
  None

• Additional Information:
  I haven't tested any other skills. It's possibly an isolated case.

[Everade]

I use a custom command to see the actual miliseconds. However since that might not be believable, i made an obvious setup that the visual cooldown indicator on the skill icons are easy to see. (just count the seconds)

Test setup as follows:
Tarot Card of Fate with a custom After Cast Delay of 10seconds.
Poem of Bragi is official, gives a -30% reduction on lvl 10.
Kiel Card with a custom value of -70% reduction.
So that would be the sum of -100% after cast delay reduction.

The results however show that there's still a roughly 2seconds after cast delay, as the official skill icon cooldown indicators in the top left show.

I hope this proofs my claims.

after_cast_delay_bug.mp4