Rathena: Lv. 5&Lv.4 NC_ARMSCANNON skill no cast time

[Surefirer]

• 1dd95bcce0e42bc62865a20b6174dcca75f4a88c:

• 20180831:

• Renewal:

• SKID.NC_ARMSCANNON skill no cast time. Not sure about KRO official behavior, but it has cast time before I updated to the lastest version of ra.:

  • Result:
  • Expected Result:
  • How to Reproduce: try use NC_ARMSCANNON level 5 and level 4, you can use the skill with no cast time, and delay.
  • Official Information:
    

• Modifications that may affect results:
  
  

[OptimusM]

This is the oficial update of Arms Cannon Cooldown.
https://ragnarok.gamepedia.com/RO_Patch_(2018_Oct._17)

[flamefury]

https://replay.divine-pride.net/Replay/d3e47f30
Made a recording for each level on a Mech.

Skill cool down added Oct17,2018, as noted by above patch link (verifiable using HEADER_ZC_SKILL_POSTDELAY packets):

• 암즈 캐논 스킬의 쿨타임이 추가됩니다.
  　1레벨 > 0.15초
  　2레벨 > 0.20초
  　3레벨 > 0.30초
  　4레벨 > 0.45초
  　5레벨 > 0.65초

After cast delay appears to be 1s for every level, can be verified by HEADER_ZC_MSG_STATE_CHANGE3 packets.

HEADER_ZC_USESKILL_ACK2's delaytime value appears to be the cast time (variable+fixed), but it's rather confusing to me. The Mech I used for that recording was 2 DEX, 3 INT. Yielded the following cast times:

1. 1839ms
2. 1816ms
3. 1993ms
4. 1970ms
5. 2147ms

https://replay.divine-pride.net/Replay/c77e63ad
Contains a replay after I upped my DEX to 131 and INT to 37. Delaytime values became:

1. 948ms
2. 798ms
3. 848ms
4. 697ms
5. 747ms

Dunno if that's enough to figure out the Fixed+Variable of each level. I'll try to math it out later.

[flamefury]

Scratch later, couldn't sleep until I solved it. I abused WolframAlpha by plugging in my cast times and stats as so:
F+V*(1-sqrt(7/530)=result1, F+V*(1-sqrt(299/530)=result2
Where F is fixed cast time, V is variable cast time
sqrt(7/530) was my stat-based cast time reduction on the first trial (DEX=2,INT=3, DEX×2+INT=7), while sqrt(299/530) was the stat reduction for the second trial (DEX=131,INT=37, DEX×2+INT=299).
result1 is the first trial result for that level, result2 is the second trial result for that level.

eg, my Lv5 calculation

Doing that for all levels gave me the following cast time results:

1. F=600,V=1400
2. F=400,V=1600
3. F=400,V=1800
4. F=200,V=2000
5. F=200,V=2200