Understanding the loot system

[revloc02c]

I understood how the old loot system worked. In the old system the lootdrop_entries table was a set of items and you could only receive one of (with loottable_entries multiplier set to 1) and the chance column was dependent on the chance values of all the items in the set. (Furthermore your chance column of the set did not have to add up to 100% even though most lootdrop sets did.)

I believe that I understood how the new loot system (http://www.eqemulator.org/forums/showthread.php?t=35770) worked too (with probability taken out). In the new loot system the chance column was a per item percentage--didn't matter what all the other chance values were in the set--the chance value was the percentage that that item would drop (ignoring droplimit, minlevel, and maxlevel for the sake of this discussion).

But now in the new new loot system probability is back and I have been testing it try to figure it out and I am not sure how it works.
How does chance work now with probability back in the equation? Is it like the old way where the chance column is dependent on the other chance values in set of items? Or is it like the new way where chance is a per item chance--with probability multiplied in? Or some other way altogether?

Or if it is easier, you could ignore the previous questions and perhaps someone could just give a good explanation of how the loot system currently works please.

[cavedude]

Probability works exactly as it did before. It is rolled to see if any item in that table will drop at all. If so, then each of the items are rolled against their individual chance to see if they will drop.

If probability is 100%, then that means the items will always be rolled. Please know that doesn't mean they will drop - that is dependent on their chance. But at the least they will be given a chance to drop. On the other hand, if probability is 1% then 99 times out of 100, none of the items will even be rolled at all and thus have no chance to drop, even if their chance is 100%.

The one part that may be confusing is in the old system, if probability rolled true 1 item would ALWAYS drop (ignoring multiplier for this example.) In the new system that is no longer true. Any number of items can now drop, from 0 to all. If you'd like at least 1 item to always drop (provided the probability rolled true!), set mindrop to 1. If you want no more than 1 item to drop set maxdrop to 1, etc.

[revloc02c]

Ah, Cavedude, thanks so much for replying. I understand now.
Probability works exactly as it did before.
From one point of view probability is the same in that it is checked first before moving on to roll against the chance column. (It is the chance roll that is handled differently than it was in the old system.) If I may respectfully offer a different point of view (not to try and straighten anyone out, but for clarification and potentially helping another who may read):

In the old system the probability represented the chance that something (specifically one thing) would drop from a set of items (like a lootdrop table of just gems). The important point here is the probability was associated with a sets of items not just individual items.

In the new system the probability is checked first, and if it "succeeds" if you will, then chance is checked. This way of doing loot is...not as straightforward as just checking loot against one percentage (like the chance column, and eliminating the probability column--as was tried in the first implementation of the new system).

The difference is in the way probability is viewed (or how loot is viewed depending on how you want to explain it). If you view loot as individuals items then the probability column does not make much sense to be sure. If you view loot as sets of items then it is the probability column that is descriptive and applicable to the set of items.

Example:
The set of gems mentioned earlier could be set up with percentages in the chance column (lootdrop_entries) according to how often you want each gem to drop. One the set of items is done it can be reused as many times as one would like for varying levels of MOBs. You can set the probability column (loottable_entries) low for low level MOBs and increase the probability appropriately for higher and higher leveled MOBs. (No need to keep creating lootdrop tables containing gems, just reuse the one you made--is one way of doing it.)

Mind you, the new system can be used similarly. Probability no longer applies to a set of items but just modifies and individual item's chance--you may get none of the items, or you might get three, or all of them if the rolls are just right. But if you want to think of the items as a "set" the overall probabilities are all the same.

The Difference:
From a statistical standpoint, the difference between the old system and the new system is that the new loot system has more variance. On average everything is the same but the fact that you could get no drops or a bunch of drops from a given MOB indicates that the variance is higher in the new system.

Consider 2 loottables each with 100 probability referencing a lootdrop table with two items that have a 50% chance each. In the old system you are guaranteed two drops from this scenario--100% from one set and 100% from the other set of items. In the new system you aren't guaranteed anything--you might get zero drops, or 1, or 2, or 3, or 4. More variance. Whether you think this is good or bad is an individual opinion.

My Opinion:
I like the new system with more variance because there's more random-ness and like gambling it turns players into Skinner rats clicking the button hoping that the next time will be the big payoff. :D

Hope this helps someone who needs it.