At some point, a triple-A studio must decide: when is it the right time to build a new engine? While the Square Enix Group studios are free to pursue their own paths when it comes to technology, Denmark's IO Interactive has always rolled its own. For 2012's Hitman: Absolution -- and what comes beyond -- the studio decided to embark on an entirely new engine, Glacier 2.

In this in-depth interview, tech director Martin Amor speaks to Gamasutra about why the studio came to that decision, and just what factors into it -- from satisfying the design team, to creating a more cinematic experience through advanced AI.

The architecture of an engine that has to support multiple titles is critical, and so is the decision-making process behind how its features are devised and implemented. Here, Amor walks Gamasutra through these and more, explaining what boundaries the team wanted to push with Hitman, and how these decisions impact the future of the technology and the studio.

Hitman: Absolution is the debut of your new technology?

Martin Amor: Exactly, yeah. We've been working on this technology for a while now and are very, very, very excited about it.

Basically, we were looking at the ambitions that we had for Hitman: Absolution and we thought, "Okay, we need to come up with something completely groundbreaking in order to fulfill these ambitions." And so we began to work on Glacier 2. Glacier 1 is our earlier engine that we used for the former games, and Glacier 2 is a completely new from, made from the ground up.

We're pretty far into this generation. How did you feel about getting a new engine ready at this juncture? This game launches over six years into the Xbox 360's lifespan.

MA: When we made the engine, it has been a big part of many of the decisions that we've made. So we made our engine in a way that we felt is trying to accommodate how we believe the future is going to be, and so we think we're in pretty good shape regarding this, for future platforms.

Also on the current generation of platforms, I still think we haven't fully explored everything that we have. There are still things to do, that we can do. We are hand-coding a lot of assembly on the PS3 to make sure that everything can get as much out of the hardware as possible. But it's kind of like a balance of effort and time, versus the cost, versus how much we actually get out of it. But there's more that can be done in this area.

I've talked about AI periodically with different people. I get the sense that AI hasn't progressed as rapidly in this generation as we might have anticipated at the outset.

MA: AI is quite complex, and I think a lot of the games, what they are challenging right now is not so much AI, but having the characters behave realistically. So you can put a lot of very complex behavior.

What we do in Hitman is also to have a lot of coordination between the characters, which is very important so they can connect the dots, right? So if one of the cops, they hear a gunshot, another cop sees a gun lying on the ground, and the third cop sees the player run away, they are able to kind of connect the dots between these events, and from that figure out what happened in this situation, and react to this in a meaningful way.

But coding the core of the AI is not the most challenging part. It's actually to have it perform realistically. So to coordinate the animations with the dialogue, and have them move around, and avoid other characters, and basically seem like real characters -- instead of uncanny valley sort of stuff. And I think that a lot of developers were kind of surprised how difficult this actually is.

It seems like it's a particularly interdependent part of the development process. It seems like with AI, art and sound design all really sort of gel together with tech, and in that specific node of character behavior.

MA: AI is kind of like at the end of the pipeline, right? Everything that all of the other developers are doing is feeding into this. The AI programmers have to work with the characters, and the animations, and the audio -- and music, not least, which is also a very important part of our Glacier 2 engine.

We have a very dynamic music system. So basically, the music system feeds into the AI, and understands what is going on, and plays music according to that -- and sound effects, and stingers, and everything like that. You're totally right -- it's the most difficult place to be, many times, is AI programming.

It's this synthesis of everything that the game has.

MA: It's also very fun. I think some of my AI programmers say they like to think that they are playing on the side of the computer, and against the player, and I think that they're having fun with that. But at the same time they have to very much focus on creating a good experience for the player.