In the talk, Chahi and programmer Ronan Bel talked about the difficult, two-year iterative process of creating a dynamic world simulation that continues to change even when you're not looking at it. "At first, I thought only part of the world could be dynamic. For instance, a river would only be processed where it's running," Chahi said. But Bel outlined how a series of optimizations allow the complex interactions of rock, sand, vegetation, water and lava to operate at a consistent 30 frames per second on the Xbox 360, PS3 and PC. "Today, computers excel in brute-force computation, so it's better to compute the whole world – no matter what is happening, the frame rate remains the same. This is very important," Chahi said.
Chahi said his team had to constantly tweak the underlying natural rules of the game world to create interesting situations, both from a gameplay and an aesthethic perspective. For example, in early builds of the game, water would cut out rivers that were incredibly deep, narrow and angular. Smoothing these rivers out took a lot of processing power, until the team was inspired to create "mud" that had the solidity of dirt but the viscosity of water. The result was very realistic river that just spawned naturally from the new rules of the game world.
While Chahi's talk was light on details of how the actual game you play in this world would work, his infectious enthusiasm for the world-building potential on display has us eager to see more at Gamescom later this week.