Resolve is the CC immunity mechanic in SWTOR’s PVP. It’s made visible by the while arc bar above your portrait and target portrait, and you can see it on a character as the white bar beneath their HP bar.

Here’s how it works:

While a target’s Resolve bar is empty or filling up, that target can be CC’d

Once the target’s Resolve bar is full (>= 1000), the bar begins to drain and the target can’t be CC’d until the bar is empty

To understand how Resolve builds, let’s look at this in-game mail from Ryndar (he’s the Sage who healed for 400k+ in his 30s, which is the highest output I’ve seen in Beta or live across servers sub-50):

Reosir and I tested Resolve stuff and thought I’d let you know what we found out (I can elaborate more in vent). Resolve provides CC immunity when it reaches 1000. The Resolve bar under the nameplates is a bar that is actually out of 800, so you’ll notice it fills but doesn’t go white right away sometimes. Stuns give 200 Resolve per second of the stun.

Mez (breaks on damage) gives 100 Resolve per second.

Knockbacks and pulls generate 400 Resolve. When you reach or exceed the Resolve threshold of 1000, 50% additional Resolve is generated for the CC ability. So a 4-second stun generates 800 Resolve and if it goes over 1000 you get an extra 400. So two 4-second stuns used back to back will generate 2000 Resolve (800 + 1200).

OK, so that gets us to the point where Resolve grants CC immunity until the bar has drained fully.

The next question is, how does Resolve drain? It depends on the state of the player in question.

If they have not yet reached CC immunity, i.e. Resolve < 1000: Resolve starts to drain when the CC effect ends

Resolve drains at a rate of 25 Resolve per second Example 1: 4-second stun gives 800 Resolve, which will take 36 seconds to drain completly (4 seconds for the stun and when it ends an additional 32 seconds). Example 2: 8-second mez gives 800 Resolve and is canceled immediately will take 32 seconds to drain (drain starts instantly if the mez ends instantly and it will take 32 seconds to drain). If they have reached CC immunity, i.e. Resolve >= 1000: Resolve starts to drain immediately when the player becomes immune

Resolve drains at a rate of 100 Resolve per second Example: 8-second mez followed immediately by a 4-second stun gives 2000 Resolve, which will drain in 20 seconds (whether you sit through the entire stun or break out of it immediately).

It’s important to note that snares (i.e. movement debuffs) and roots are not factored into the Resolve system. That is, they do not build Resolve, and their effects still apply to targets that have CC immunity.

The Resolve mechanic is the most elegant CC immunity / DR (Diminishing Returns) mechanic I’ve seen in any game, because it provides visibility into the immunity state of your target, when they will likely go immune (e.g. next CC applied), and how long they will be immune for. You can also “game” your Resolve to know when to pop your CC breaker.

In some games CC immunity / DR is tracked by the game but not made visible to the player.

As I’ve said elsewhere, SWTOR provides the highest skill-cap in terms of PVP for any game I’ve played, and the Resolve mechanic is another example of elegant, innovative design by BioWare.

UPDATE (2011/01/10): added drain rate information, per testing by Ryndar and Reosir.

UPDATE (2012/01/26): added notes about snares and roots and for abilities that apply multiple Resolve-building effects.