http://jalopnik.com/5808738/how-forz...ulture-forever
it's a really good read. I've just included some snippets.
some clips:
"For starters, Turn 10's re-rendered every single vehicle, ripping the graphics engine down and building it back up. And the results are simply staggering. Polygons per car are up from Forza 3's 400,000 to over one million polygons per car in Forza 4. Turn 10's added real-light changes like blooming and lens flares help make the cars look like they're really in the environment. Forza 4 is achieving in real-time at 60 frames per second what was once something Pixar needed weeks to render."
"Not only has Turn 10 rebuilt the physics engine from scratch, they've also tried to address one of the most glaring problems with Forza 3, the tires. That's why, for enthusiasts anyway, the most important addition to the game is going to be the tire physics. Thanks to a partnership with Pirelli, Turn 10 has completely redone the modeling for tire dynamics. The tire company let them inside their testing system to give the game a soup-to-nuts data download and allow them to directly input it into the game."
"One of the coolest new community features is the ability to create a guild-like car club and then recruit your friends or, really, the best of the best and have the ultimate dream team of drivers, tuners and painters from the "Forza" community. Within each club you'll be able to share your custom cars and then, if you're interested, use them to dominate the other clubs. "