"I guarantee that this game couldn't be working on XBox 360. It would be impossible. I'm 100 percent sure of this." Christophe Balestra, co-president of Naughty Dog, spoke with Ars about the technology behind Uncharted 2, the hugely anticipated follow-up to one of the PS3's best games: Uncharted: Drake's Fortune. "First of all, we fill the Blu-ray 100 percent, we have no room left on this one. We have 25GB of data; we're using every single bit of it."

Naughty Dog is owned by Sony, and while the developer makes wonderful games, it's very clear why we were there: to talk about the power of the PlayStation 3.

Balestra pointed out how important it is to ship every system with a hard drive. "The fact that every PS3 has a hard drive is huge for us." He went on to describe how the game takes advantage of Sony's offerings. "It's the combination of Blu-ray and hard drive. You can play the entire game without loading. We don't require an install. We're doing all the post-processing effects on the SPUs [Synergistic Processing Units]. The quality of the depth of field we have, you can't do that on the Xbox."

He was blunt about what Uncharted 2 means for the PlayStation 3. "We've invested a lot of time maximizing the power of the machine," he stated. "That's our job, to make the PS3 shine."

What they've learned

For the first game, Balestra estimated that they used around 30 percent of the power of the SPUs, now the team was able to use them to 100 percent capacity. Naughty Dog understands the Cell processor, and knows how to get it to sing. "The ability to use the RSX [the PS3's graphics processor] to draw your pixels on the screen, then you use the Cell to do gameplay and animations—we kind of took the step of using the Cell process to help the RSX . All those things are done on the Cell processor," he explained. "It really helps us getting that quality of lighting per pixel; the amount of computation is pretty crazy."

Naughty Dog also used the SPUs to add physics to the sound so things occlude properly. That means that if you're behind a door, the sound will reflect that. Effects will sound different depending on where your character is in relation to the source. "All that math is done on SPUs to immerse players into the environment," he said. If you have a surround-sound setup for your PS3, this could very well be your new showcase title.

The other improvements from getting closer to the metal with PS3 development will be more easily seen by even those without high-end audio systems: better performance, and better AI. "We had a pretty good AI system on Uncharted, but we wanted to have more [non-player characters], we wanted to have also more enemies on the screen."

All this goes on behind the scenes, but it leads to a game world that feels real. The characters react realistically to what's going on, the sound is shaped by where you are and what you're doing, and the amount of action Naughty Dog was able to put on the screen is impressive; the set pieces we've seen from the game so far look more like a heavily choreographed film than something that's interactive and playable. It takes a lot of horsepower to make that happen, and Naughty Dog now has the experience to squeeze every drop from the PS3.

Being first-party has its responsibilities

Uncharted 2 is going to be a showpiece title for the PlayStation 3, and Balestra notes that the knowledge and technical know-how used to create the game is something the team shares. "One thing we did for Uncharted is that we made the source code available to all the first parties," he explained. There is a team at Naughty Dog that's separate from those working on the game; their mandate is to work on technology that's shared with both first- and third-parties.

"They know how we're using the SPUs; they are free to look at how we're doing things and package it in such a way that it can be shared with third parties," Balestra told Ars.

Developers from Naughty Dog give talks at GDC, and the team often has third-party developers coming into the offices to discuss PlayStation 3 tech. Balestra said they have time set aside to speak with other developers after the game is finished—as of this writing they're nine days away from submission.

"We're very open, yes. That's part of our jobs."

All this technology serves one goal: to make a good game

It's hard to think about the technical aspects of gaming and still keep one fact in mind: if it's not fun, all that work is for nothing. Thankfully, Uncharted 2 has personality and character to spare. We asked Balestra to name the one thing he wanted to improve from the first game, and he became somewhat philosophical.

"Sometimes people ask us about what is the one thing [we improved] on Uncharted 2, and it's hard to answer. We're trying to increase the quality of the game, so we're design-driven. No matter what it takes, we'll find a way to figure it out, to squeeze what we need to squeeze out of [the system] to make it happen."