I have noticed this issue for a while now and figured it may be time to start looking into some possibilities to make loot tables work a little better. As it is now, it seems like the loot table system isn't nearly as random as it should be.
From what I can tell, the code pulls the loot tables and then it sorts the drops in the tables by the chance they are set to. After that, it then uses random 0 to 99 and goes down the list from top to bottom seeing if one of the items gets the right random needed for it to drop and then it stops. I think this creates a problem because having them sorted the same way each time means that the ones at the top of that sorted list are always more likely to be chosen than ones at the bottom of the list.
As an example, lets say we have 10 items all with a 10% chance to drop. It will then start at the first item in the sorted list and start randoming 0 to 99 and once it gets a number in the needed 10% range, it stops. So, even though it seems like it should average out to be random, it doesn't seem to be working that way. It is giving items at the top of the list a considerably larger preference than ones at the bottom of the list. Which means you will see the ones at the top of the list drop much more often than any others.
From everything I have seen so far while testing in game, it seems like it sorts the output alphabetically and so anything starting with lower letters in the alphabetical order is more likely to drop than others.
I marked the section that I think is responsible for the way that loot tables are currently created in
RED in the code below.
loottables.cpp
Code:
// Queries the loottable: adds item & coin to the npc
void ZoneDatabase::AddLootTableToNPC(NPC* npc,int32 loottable_id, ItemList* itemlist, int32* copper, int32* silver, int32* gold, int32* plat) {
_ZP(Database_AddLootTableToNPC);
//if (loottable_id == 178190)
//DebugBreak();
const LootTable_Struct* lts = 0;
*copper = 0;
*silver = 0;
*gold = 0;
*plat = 0;
lts = database.GetLootTable(loottable_id);
if (!lts)
return;
// do coin
if (lts->mincash > lts->maxcash) {
cerr << "Error in loottable #" << loottable_id << ": mincash > maxcash" << endl;
}
else if (lts->maxcash != 0) {
int32 cash = 0;
if (lts->mincash == lts->maxcash)
cash = lts->mincash;
else
cash = (rand() % (lts->maxcash - lts->mincash)) + lts->mincash;
if (cash != 0) {
if (lts->avgcoin != 0) {
//this is some crazy ass stuff... and makes very little sense... dont use it, k?
int32 mincoin = (int32) (lts->avgcoin * 0.75 + 1);
int32 maxcoin = (int32) (lts->avgcoin * 1.25 + 1);
*copper = (rand() % (maxcoin - mincoin)) + mincoin - 1;
*silver = (rand() % (maxcoin - mincoin)) + mincoin - 1;
*gold = (rand() % (maxcoin - mincoin)) + mincoin - 1;
cash -= *copper;
cash -= *silver * 10;
cash -= *gold * 100;
}
*plat = cash / 1000;
cash -= *plat * 1000;
int32 gold2 = cash / 100;
cash -= gold2 * 100;
int32 silver2 = cash / 10;
cash -= silver2 * 10;
*gold += gold2;
*silver += silver2;
*copper += cash;
}
}
// Do items
for (int32 i=0; i<lts->NumEntries; i++) {
for (int32 k = 1; k <= lts->Entries[i].multiplier; k++) {
if ( MakeRandomInt(0,99) < lts->Entries[i].probability) {
AddLootDropToNPC(npc,lts->Entries[i].lootdrop_id, itemlist);
}
}
}
}
I definitely think that loot tables could be done much better than the way they currently are. Here are some suggestions:
1. Randomize the order of the list of loot drops each time before it starts going down the list to do the random 0 to 99. This should ensure that no item gets preference in a list of equal chance drop rates. To make sure this works to make the list as random as possible, you would also need to get the count of how many different percentages are set. So, if you have 3 set with 25% each and 1 with 15 and another with 10, the count would be 3 different percentage drop rates. Then the system would need to randomly select which percentage to use first instead of just always starting on either the highest or the lowest percentage.
If the order of the table was randomized first (maybe using a hash), you should be able to set all items to have 100% chance and it would give each item an equal chance of dropping, since it would randomize the list and then chose the first one on that randomized list.
2. Assign a number range to each item in the table at the time the loot table is created so that the total is from 99 and then random the 0 to 99 and pick whichever item is already set for the range that the random number landed in. So, if you have 4 items each with 25% drop rate, it would assign the first item from 0 to 24, second item from 25 to 49, 3rd item from 50 to 74 and the 4th item from 75 to 99. And if the random landed on 55 it would chose the 3rd item. This also works well for lists with multiple different chance drop rates. You could have 1 item with 50% chance, another with 25, another with 15 and 1 with 10 so that it totals 100%. In this scenario, it would assign 0 to 49 for the first item, 50 to 74 for the second, 75 to 89 for the 3rd and 90 to 99 for the 4th. Then, if the random landed on 78, it would chose the 3rd item in that list.
I think this would probably make the best solution, but I don't know how hard it would be for it to create the lists I described. Plus, if the total chance in the table didn't equal 100, it would cause problems and would need additional code to correct it. As long as it was less than 100%, it could just random again and again until it landed on the right percentage range. Or, it could just end there and not give any loot (might be good for setting extremely rare drop rates). But if the total was more than 100%, I am not sure exactly what the best way would be to deal with that other than totaling the chance drop rates and dividing them so that they total 100%. So, if you had 4 items all set to 100% chance then it would total it and see it equals 400%, so it would divide each drop chance by 4 so that the total was 100% as it should be and it turns each chance drop into 25% as they should be. If there was a way to make that work, it might be nice for loot tables that have multiple items that should all have equal chance to drop. Then instead of having to break out a calculator to figure out how to total 100 with 7 drops in the list, you could just set them all to 100 and let the loot code do it for you automatically.
If the code could figure out what to divide by to equal 100%, it should work in all scenarios. So, if you have an item with 75% chance, one with 50% chance, one with 25% chance, the total would be 150%, so the code would know to divide each chance by 1.5. So in this case, the first item would equal 50%, the second would be 33.3 and the 3rd would be 16.6 and the new total would be 100% as it should.
3. Another option might be to have it random once for every item in the table and then if more than 1 equals the random number, it would random again between the list of items that were selected by the randoming process. So, if you have 10 items each set to 10% drop chance, it would go down the full list and maybe 2 or 3 items would be selected due to the random number landing in their percentage range. Then it would randomly chose one of those 3 items. This way it should ensure that items at the top of the list don't get any special preference as all drops get a chance to be checked if they can be selected by the 0 to 99 random.
Also, I am not sure but I would think that it should be randoming from 1 to 100 instead of 0 to 99. Maybe I am missing something there, but I don't see how 0 would factor in on the randoms other than to make 0s a fail so that it moves on to check the next item.
Either way, I think the loot table code definitely could use some tweaks to make it work better. I will see if I can find anything to maybe help some, but as I have said before, my coding skills are not so great just yet. If anyone feels like chiming in or helping with this, it would be appreciated
Loot Table Problems
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