Now that the chaos has died down a bit, we've had a chance to pick through the trailer to see what kind of technical upgrades might be hiding under the proverbial hood of GTA IV. Note, these aren't all confirmed features, per se, but they do seem to indicate things will, in fact, be different.
Perhaps the most obvious technical upgrade visible in the trailer is the real-time lighting and shadows. Now, seeing as this is a next-gen title we're talking about, one might say this feature is a given. However, after experiencing and modding the GTAIII Trilogy, I think this deserves a lot more attention than it will probably get.
In every title since GTAIII, all the environmental lighting has been done by pre-lit vertices. For those not technically inclined, this basically means the highlights and shadows were painted into the models, then multiplied all together to roughly match the time of day.
While the results looked good at any given moment, as time passed by things just didn't seem alive. With real-time lighting, on the other hand, the "living, breathing city" concept of GTA has just gotten a whole lot more dynamic.
Another possible no-brainer for a modern title is normal mapping. But considering the history of somewhat blocky peds in the series, and if this is what we think it is, it is a welcome change.
If you look closely around the arm and face of this ped, you can see that the lighting appears to be smoother than the actual polygonal mesh. This trick is done by creating a smooth, highly detailed version of a 3D model, rendering a texture which stores the vertex info, then applying it to an optimized version of the model.
The end result is a more detailed model with a much smaller file size. Which of course is a good thing when you've got a dozen or so on the screen. It also looks as if both peds in the picture have individual fingers..
One of the most annoying and downright bizarre things about the series has been that it's seemingly inhabited by an army of clones. Granted, San Andreas fixed this a bit by adding tons of different peds, but nevertheless, one would always run into the same person in the same clothes over and over again. Day after virtual day.
Hiding amidst the time-lapse portion of the trailer though are clues that this may be about to change. To the left are a series of screenshots from the trailer showing an otherwise identical person wearing mixed and different color outfits. If you go through the trailer frame by frame, it seems that there are a bunch of other peds wearing random outfits.
Yes, it is possible that they are four unique ped models. But after the player clothing options in San Andreas, it's only natural that Rockstar North expand this to peds. And if that's really the case I would expect the variety to grow even more as the game draws closer to completion.