The math behind loot drops

When it comes to any sort of MMO there is never universal agreement on what frustrates players. There is, however, agreement on individual things that do frustrate us all. One of them is “broken” drop rates.

I am a big advocate of things making sense when it comes to loot generation. In fact this has been the topic of several of my articles. I really took a narrow focus when looking into Warhammer Online’s city dungeons and Lost Vale. It is fair to say, at least in those areas, the method by which loot was/is generated was/is frustrating.

The irony about all this is that I am now playing the role of developer on Shadow Realm. Instead of being the one pointing out that drop rates and loot generation is not that fun I’m the guy receiving all the un-pleasantries. EverQuest, after all, was designed in part on a pretty rough system.

I think the best thing to do, at least in these situations, is be clear about how a system works. I know I feel less violated by a system when I at least understand how it is doing the dastardly deed. My players still don’t seem to understand the cogs and gears behind the curtain. It is time to take a moment and explain the system and then relate it to a production MMO. I’ll be using Warhammer Online today.

When you’re on the Shadow Realm and defeat a mob the server takes a look at the mobs loot table. In that table it will look up the various loot drop IDs that are there. To clarify this: loot drop IDs are not items. They represent a “pool” of items. In each pool you will then have individual items.

Each loot drop ID, before we ever get to the items, has a chance of occurring. Let’s imagine that we’ve gone off our rocker and decided to kill a Gnome Slayer. Obviously this is a crappy thing to do since the world needs more gnome slayers. The Gnome Slayer has three loot drop IDs, (Alpha, Bravo and Charlie). Alpha has a 100% chance of occurring while Bravo only has a 50% chance. Charlie sneaks in with only a 10% chance.

When we kill a Gnome Slayer the server sees that since Alpha is a 100% chance it will occur. The game then flips a coin (so to speak). Heads says Bravo occurs and on tails it doesn’t. It then rolls a ten sided dice. If ten comes up than Charlie occurs. For our example we’ll say Alpha and Charlie occur. All of these rolls are all totally independent of each other. Each roll does not and never will affect the other.

Now that the game has decided loot drop ID Alpha and Charlie will occur it looks at the items in those pools. Loot drop ID Alpha has only one item, A Letter of Commendation. As such, that item has a 100% chance of dropping. Loot drop ID Charlie, however, has four items: a gnome head, a short sword, a rock and a football. Each item can be weighted in any way as long as the total chance adds up to 100%. For this instance we’ll say 25% each to make things fair. The game rolls again and picks the appropriate item. For our example we’ll say a rock because anyone who slays a gnome slayer doesn’t deserve loot.

All of this occurs, of course, without player knowledge. So, when they kill a Gnome Slayer and kneel on the corpse they see A Letter of Commendation and a rock. If the loot drop ID has a large pool of items that can, obviously, lead to frustration. Repeat drops are, in general, a likely occurrence.
This is exactly the situation that Warhammer Online found itself in when it came to city dungeons and Lost Vale. The loot drop ID was clearly 100% when it came to the ward armor drops but the pool was far too large. We would frequently be presented with the same or useless drops. Even when we would get two chances at an item it didn’t matter. The game simply rolled twice on the same table independent of the first. Suffice to say it was frustrating.

I now find myself in the same situation with Shadow Realm. Any thing that I design I ensure each loot drop ID has no more than five total items. I, however, have inherited a ton of content that does not conform to my rules. It is simply too much content for a single developer to go back through and correct. So I just have to take the fire and say, “Yes it is working right.” After all, it is working right. It just sucks.

What is important about this? I hope it is another example to future developers. Modern MMOs shouldn’t use this type of system! Keep loot tables small or use tokens, armor blanks or something similar. Most of us don’t like killing the same mob over and over again. This is doubly true if we’re max level.