Terminus Weapon Roll Algorithm¶
Terminus Weapons are drops from the 'The Tale of Bahamut's Rage' quest (ID 407318).
It may reward an exclusive weapon for a random character (post-release characters do not have a Terminus weapon.).
Tip
TLDR: Chance to get ANY weapon is always 20%. The chance to roll for a specific character becomes higher the LESS characters you have unlocked. You can only roll for characters that you have unlocked. You cannot have more than one character's terminus weapon.
Relevant game tables:
rewardreward_lot
First, the quest's base info file declares that it will use the following chests on completion (treasures, in treasureData_):
RW_407318_400RW_407318_401RW_407318_402RW_407318_403RW_407318_404
RW_407318_400 is the chest where one of its 5 reward 'lots' are the terminus weapons, as per the reward table. This row has Lot1ExclusionChance, which specifies that its first lot will have a 80% of being excluded.
This translates to 20% chance of appearing, or 1/5.
Heading to reward_lot with key 1BF30AB2, we can see the list of all weapons.
Whenever WeaponId is set, the game treats the lot as being rollable only if that weapon hasn't already been rolled, and the character has already been unlocked.
The game iterates though the list of reward lots, makes a sum of the Weight column for all available weapons & their character.
A random number is rolled which we will call value = rand() % totalWeight.
It then iterates through rows again, checks if the lot is available again (otherwise goes to the next one), and checks if value is below the current lot's weight. If so, the weapon is then rolled, and the entire algorithm for that lot ends. This ensure that you cannot roll more than one weapon. Otherwise, value -= current lot's weight, and moving on to the next row.
Note
There is special hardcoding to handle Gran/Djeeta as one single weapon/character. (Most of the game does this when it comes to captain, checking maaaany times for Gran or Djeeta's character code).
Full Algorithm¶
This is the full reverse-engineered algorithm dumbed down and simplified into pseudo-code.
get reward row from quest's reward id
get reward lot 1 with Reward->RewardLotId1 IF lot exclusion chance % is not set, or a random % number is above it
// start establishing a list of eligible items (by building total weight)
set TotalWeight = 0
foreach reward lot where reward lot = reward lot id
check if should give weapon:
// StoryDiff 3 = Ultimate.
- check if (storyDiff == 3 AND curRewardLot->StoryDifficulty == 3) or (storyDiff != 3 AND (curRewardLot->StoryDifficulty == -1 OR curRewardLot->StoryDifficulty == storyDiff))
- check if curRewardLot->RewardRank == -1 OR curRewardLot->RewardRank == currentRewardRank
- check if already has weapon in save (weapon id)
- check if character is unlocked by grabbing get WeaponData->CharaId and checking in the current available character list (in save)
if check pass all above
TotalWeight += currentRewardLotRow->Weight
if TotalWeight == 0
return // no reward.
set chance = rand() % totalWeight
foreach reward lot where reward lot = reward lot id // (again)
check if should give weapon (same checks)
if chance < currentRewardLotRow->Weight
push weapon reward lot in list of rewards
return // done. bail early because we don't want to give more than one.
else
chance -= currentRewardLotRow->Weight
// do the same for Reward->RewardLotId 2/3/4/5/6 if they are set, without exclusion check (reserved to lot 1)
Function signatures:
void RewardManager::GetReward(RewardManager *a1, void *a2, unsigned int rewardLotId, unsigned int storyDifficultyType, int rewardRank, char a6);
41 57 41 56 41 55 41 54 56 57 55 53 48 83 EC ? 48 89 54 24 ? 8B 69
bool RewardLotData::ShouldGiveWeapon(RewardLotData *a1, uint storyDifficultyType, int rewardRank)
41 56 56 57 53 48 83 EC ? 0F B6 41
bool WeaponManager::HasWeapon(WeaponManager *a1, uint weaponId)
56 57 4C 8B 41
Decompiled code: https://gist.github.com/Nenkai/4111b4fb44e3c00aadf4245e4f581c43