Friday, September 22, 2006

The Arena Rating System (Updated)

This post was originally done a couple months before the release of the The Burning Crusade. I was lucky and my combination of guesses and research turned out to be a pretty accurate overview of how arena ratings were calculated. Unfortunately, just like the other PvP systems in World of Warcraft the arenas were vulnerable to exploitation. This quickly became a major problem since the arenas offered the best rewards which made them a much bigger target then battlegrounds. Blizzard has had to modify the arena system several times to try to fix exploits and my original write-up has become way off base. So after looking at the Season 4 patch notes and comments I decided to update my arena write up.

Team Rating
The initial arena system was based on the ELO chess system where teams had a rating that changed depending on the toughness of their opponents. I'll leave the basic explanation of team ratings the same since they haven't changed that much. Team ratings are still primarly how arenas points are rewarded and how team's are matched up against each other. Players who have used holes in the arena system or switched between a lot of different teams will find that their personal rating is used instead of their team rating.

Lets have team A and team B who meet in the arenas. Team B has a moderately higher score then Team A which means their odds of winning are calculated as being higher for the match. This means that Team B's rating will decrease more if they lose and increase less if they win. Team A's rating on the other hand will do the opposite. There is also an arbitrary number in the formula which decides the maximize number of points lost or won for the match. I'm using the number 30 but honestly this number probably changes based on the rating difference between teams.

Team A's Current Score: 1500pt
Team A's Chance of Winning: 1500 / (1500 + 1580) = .48701

Team B's Current Score: 1580pt
Team B's Chance of Winning: 1580 / (1500 + 1580) = .51298

Now Lets say Team A won the battle then
Team A's New Score: 1500 + (30*(1-.48701)) = 1500 + 15.39 = 1516
Team B's New Score: 1580 + (30*(0-.51298)) = 1580 + -15.39 = 1566

Now Lets say Team B won the battle then
Team A's New Score: 1500 + (30*(0-.48701)) = 1500 + -14.61 = 1485
Team B's New Score: 1580 + (30*(1-.51298)) = 1580 + 14.61 = 1595

Personal Rating
Personal Rating works just like a seperate version of the Team Rating for each player who actually participated in the match. Blizzard put Personal Rating requirements on certain rewards because highly rated arena teams were selling spots to people who wanted to quickly gain points. Each player actually has a Personal Rating for each of the arena brackets in the game. Thus a person could have a very high 2v2 personal rating and an average one in the 3v3 and 5v5 brackets. If a player switches team then their personal rating for that bracket is set back to 1500.

New rules for Season 4 (May 2008) actually use the personal rating for matching and point rewards over the team rating.

- If a character’s personal rating is more than 150 points below the team rating, they will earn points based on their personal rating instead of the team rating.
- If the average personal rating of the players queuing for a game is more than 150 points below the team’s rating, the team will be queued against an opponent matching or similar to the average personal rating.

Awarding Points
Blizzard has an arena calculator on their website which can be used to tell how many points your team will earn with your current rating. Only teams that have played more then ten games that week will be awarded points. Also only players on that team that have participated in at least 30% of the matches will get points.

Arena Exploits being Addressed in Season 4

Smurfing is the practice of creating smurf teams by taking a well equiped arena player and putting them on a team with a low rating. These players then artificially inflate the rating of the team and then switch back to their main team. They then use certain methods to make sure they play their smurf team which throws the match. The method works especially well in the 3v3 bracket which is easier to control the matching then the 2v2 bracket and doesn't require as many players as the 5v5 bracket. The new changes for awarding points based on personal rating will of course penalize teams that have players that frequently change teams.

Arena Scouting
Also Blizzard is making a change to arena scouting which is commonly used to make sure their opponents are a smurf team instead of a serious challenger. This method is also used in Win Trading where teams make aggreements to lose a match against a certain opponents. In general Arena Scouting is used at low population times when very few teams are in the queue. This allows arena teams to be fairly certain if both their queues pop at the same time that they are going to be matched together. If one team's queue pops before another then they re-queue.

- "If a team does not enter an arena match that is starting they will lose points equal to the amount that would have been deducted if they had played and lost."


Slant said...

Interesting read, thanks. I wonder how the strength of a team is calculated. Maybe if a Tier III equipped char brings a blue geared char to battle, how will that effect the rating?

Ferial said...

Slant - if it's truly inspired by the ELO system, then it will be based entirely on win/loss ratio and not on what gear a character brings to the battle.

That said, I think it's obviously possible to game this system - go look at Yahoo! Chess as an example - although I don't think it will happen in the way you're describing. Look instead at Halo 2 on XBL and how their rating system works - it's very similar to this, and yet has the interesting trait that there is a *remarkably* small number of people at the higher ranks. That's because there are only a few people that are good enough to beat everyone else so consistently, especially when they're grouped against people who have already proven to have a similar prowess for the game. I expect most teams will reach a plateau in their rank far before the incentive to just quit while they're ahead kicks in.

slant said...

I see, I was heavily focussed on PvP last year. We were running WSG quite well.
The Problem at some point was that there was only a limited amount of players for certain ranks. ANd at some point you had to compete with your own teammates.
Since I was working while some others had additionally the afternoon to gain honor over me. So at Rank 11/12 I hit a brick wall were it was no longer possible to catch up with them unless handling out a deal, like it is being done at the moment.
I am just interested if the new system would give players that can only PvP 6-8 hours a day a fair chance to get good rewards.

Anonymous said...

From what I understand, to remain competitive a team has to play a minimum number of matches per week, otherwise their rating will decay, and lower rating means lower possible points earned. Their points earned don't decay however, which is the important part of a pvp system that isn't as much of a chore as the current one.

Relmstein said...

Just some updates:

Minimum amount of matches a team has to play to get points per week: 10

Percentage of battles a member of a team has to play to get points: 30%

The matching system will match teams together based on those that have similar scores and not gear. Other then that the matching system will not directly effect the ELO style scoring.

Anonymous said...

Take a look at:

Lets assume that Blizzard uses the same constants in the ELO formulas:

Then team A's chance of winning is 0.39

If team A won the new ranks are:
team A = 1520
team B = 1560

If team B wins, things become:
team A = 1488
team B = 1592

What is unclear what ferial referred to. Is blizzard using the win/loss ratio in a given week or the number of wins and losses in a given week? That changes things...

DP said...

Here's my question:
When is your rating turned into Arena Points? weekly? Ive heard the idea of "seasons" thrown around, as in you get your points at the end of a season.

Anonymous said...

its not inspired by elo-system.... not just the idea of an elo-system...

it is a 100% working elo system, implemented with all rules and formulas an elo-system needs.

your rating will change immediately after each game. but it will change a bit slower than in other elo-systems... elite chess players play perhaps one tournament per month when they are very active, in WOW arena you can do the same number of games in 1-2 hours.

there is no reason to play more than 10 games per system per week. the strategy is: be perfectly prepared. you need to be in a good shape and concentrated, then you do some warmup games until you feel ready for the real thing, and then you play. as soon as you get a good scoring you stop playing until next week.

continue winning rows, and when youre losing too often the team should immediately stop and go practising and try again later.

the worst mistake would be: just playing arena hours an hours without preparation or practising. 20 grinding hours per week will get you less points than 2 perfectly prepared hours per week with teamspeak, warmup practising, and the best possible strategies.

the winning teams will be teams that spend 95% of their time for practising and for getting the best possible gear (regular pvp and highend pve, best possible sockets and enchants, members of elite-guilds and/or highly skilled pvp-players). practising will be very important. then, when everybody is in the right mood and 100% concentrated these teams will join the arena for a short time and crush their opponents, trying to get a large winnig row, and repeat this every week.

Anonymous said...

But don't forget, it is just a game...

Jon Hanks said...

For anyone not wanting to do that crazy math There's also arena calculators available.

Relmstein said...

This post is horribly out of date and it still gets linked to a lot. Think its almost time for an update.