Density

I'm sure there's probably a more official "game design" term for this, but I like to call it Density, or how densely packed the players are in a play space. Almost every game has some aspect of this, Battlefield Conquest maps have larger areas, more outposts as player sizes increase.  A COD map has a much smaller area and typically more constant and consistent action. While it may seem insignificant on the surface, this actually shapes the moment-to-moment gameplay.

Massive Scale Brings Massive Challenges

This concept is particularly important to Open-World MMOs such as PlanetSide and PlanetSide 2. Lets assume you have a 8k x 8k area, with 1500 people somewhere in that area.

First, the density range is itself a problem. 1) That's about 23 players per square kilometer if they were evenly distributed - far larger than most FPS maps. 2) In the other direction, you can have 1500 players in a single square kilometer (or smaller) if they were to all gravitate to one area. For #1, your problem is players are too spread out and not interacting. For #2 your problem is that so many players in one spot grinds the server and framerates to a halt. So you can't have players too spread out, and you can't have players all together.

The density itself changes the gameplay. Some weapons become problems at high player counts in tight areas, like grenades. Some players like smaller fights; some want huge fights. Most just want any decent (i.e. reasonably balanced population-wise) fight.

There's also the problem of population & persistence. The population isn't fixed at 1500. Sometimes it may be maxed like at prime time; other times it may be very low, like at 4 in the morning where you may have 1/20th the population. Yet your map is still fixed. That is the fundamental challenge of a persistent world large-scale MMO - the map is fixed, but the player count isn't.

And finally you're up against Free Will. Players can go wherever they want. You have to convince them (willingly for the most part) to fight in the desired densities, and to do so in reasonably fair numbers, without them feeling "forced" to do things. Which is tough, because gamers always feel "forced" by the devs to do stuff. :)

And if that isn't enough - this is all further exacerbated when your primary content is PvP - you need players to interact in order to have a game experience. When players come in and don't find good interaction they will quickly get bored and leave.

All of this combines into a perfect storm of challenge to make a game like PlanetSide 2 actually function and be fun. And for all its faults, it's still going after 4 years when many other more traditional games have come and gone and didn't even last a month on our machines. I think it's important to remember that PS2 has outlasted a yuge number of games.

OK so hopefully I've got you thinking about something you hadn't considered before and I convinced you it is extremely important to get right. So now onto some of the macro approaches to stabilize density, make it flexible, and have a game that actually creates many of these experiences. You'll recognize a lot of them i'm sure.

Most games control density very simply - they fix the player size and fix the map size (they constrain it), and then use gameplay and objectives to focus the players into key areas to create/entice conflict. Things like power-ups, capture points, terrain bottlenecks, etc are all examples of ways to manipulate the density to create the conflict you want. And if its' too tight - make the map bigger. If it's too sparse, reduce the number of objectives, or reduce the map size, or both. Some games like RPGs us phasing tech to keep density from getting too high. A lot of that isn't easy for PS2 given the scale and fixed persistent maps, so we have to be more creative. Lets look at some of the tools PlanetSide 2 uses.


Continent Locking


When you have a massive open persistent world, your options on controlling density are a lot more restricted. You usually can't just cut down the active map space - you could have many places relevant, and that would ruin the whole point of the large scale.  In PS2, an example of cutting down the active map space is Continent Locking. If you lock a continent and another doesn't open up, you've closed the active map space and forced remaining players to converge to the remaining open continents. The important effect is that have increased density while also providing a intermediate victory condition to an endless war. If you have the right size and count of continents, this could be a very good way of handling population fluctuation and stabilizing density. That was largely how continent locking helped PS1; at prime time, 6-8 continents would be unlocked and decently active, and late night it typically converged down to 1-2.

This is the same function continent locking serves in PS2, however the map sizes are much bigger than PS1, and the continent count much smaller. It's less-granular, so there's higher density variability. Still, when you have very low pop, like on servers like Briggs where only one continent is open most of the time, we have effectively limited the active map to 25% of what it was before continent locking. That's a huge difference for Briggsers.

I've always thought that the PS2 continent locking approach wasn't aggressive enough. This is one area that could use more tuning.


Lattice

Another way to increase density without constraining the map space, is to reduce the number of actionable objectives. This is fundamentally what the lattice does at a macro-level. It takes what could be 90 different objectives and reduces it down to a much smaller amount. While the entire continent is being contested and is playable, only a subset of it is actually in play. This preserves the scale of the game and its large area while still serving to increase and stabilize the density.

Lattice serves a second purpose, and that is to also funnel and force conflict. Early on in PS2 there was no lattice, and players often skirted right around each other, even large zergs because there was nothing that forced them to fight over a territory - if it looked too tough or couldn't be steamrolled just ignore and go around. They had 3-4 other choices typically and would avoid each other for the path of least resistance. With the lattice, avoiding the enemy is much more difficult. When the feature first went in it was immediately obvious as the combat intensity increased quite significantly.

Number of links, or level of constraint int he lattice, is a key tuning knob. Too many links and the lattice loses a lot of it's density stabilizing properties. To few links and the game feels incredibly constrained. For PS2 this was largely a trial-and-error process and resulted in 3-4 links per territory typically. For PS1, with it's smaller continents, the lattice was very tight, typically 2-3 links at most facilities.

Lattice also has the effect of accenting persistence, because there's chunks of territory off-limits, and territory is not constantly changing hands all over the map. That makes the map more stable, and the feeling of conquest more meaningful than a fleeting capture that will flip another half dozen times in the next hour.


Player Mobility

A key impact of density is also player mobility. Players moving rapidly around the map destabilizes fights, and causes density to be highly variable, to the point where you can't actually get stable fights or a stable front. This can be mitigated somewhat with a more restricted lattice so there are fewer meaningful places to jump to, leading to more stability.

It is important to understand that the goal in controlling mobility is not to prevent players from going where they want to go; it is to encourage them, on the whole, to generally not bounce around in significant numbers in a short period of time and destabilize engagements. That means doing such rapid movement may not be easy or convenient, or it may take a few minutes to do.  While players often want to go where they want right at that instant, it isn't a good thing for the game when everyone can and does exactly that. A good philosophy is to let them do what they want to do, but have meaningful consequences for their choices. Stable density = easy & free, volatile density = difficult and expensive.

Features like reinforcements needed and instant action can provide mobility to players while stabilizing density (when they work correctly!). The idea is pretty simple - offer mobility, but limit the choices to places that help stabilize density. Of course when 50 players all use it simultaneously you have a problem. The never-built resource revamp had some means to address that.



Those familiar with my history in PS2 will notice a trend in these features - they are all features I worked on and tuned at some point in PS2's development. At the most fundamental level, density is what I consider the most important macro-scale element for a MMOFPS game such as PS2. It is what sets the stage for your entire game experience and shapes the success of the product.

With continent locking, lattice, and controlled mobility, you take a giant mess that is an open persistnat world with 75-100 objectives and turn it into a series of typically reasonably balanced fights. It's far from perfect, but PS2 is a pioneer in a largely uncharted genre. It takes time to get it right, and as with all innovation there's often a lot of failure before you find success.