GTA4 is making a significant leap from the previous titles in the series. The developers are comparing it to the jump from GTA2 to GTA3.
Gameplay
* Niko can use a mobile phone to receive calls and phone his contacts. He can also use it to call taxis and purchase weapons. The options presented on the phone's LCD are Phonebook, Messages, Organizer, and Camera. The phone is also used to enter cheat codes.
* Pedestrians smoke cigarettes, read books and newspapers, drop litter, talk on mobile phones, walk in and out of buildings, and generally act like any normal pedestrian would.
* It is possible to climb exterior fire escapes.
* There are many different animation sets for breaking into cars. One of these involves Niko smashing the side window with his elbow, climbing into the car, and then hot wiring it.
* Niko can check his current balance at ATMs.
* GTA IV features multiplayer, but it's "not a massively multiplayer game," according to Rockstar's creative vice president Dan Houser.
* Cracks exist on a car's windscreen after being shot at. They no longer shatter unrealistically like in previous GTA games.
* It is possible to surf the internet in GTA4 via internet cafés. It is available from any computer in the game, and provides a hub for all sorts of interactivity within Liberty City.
* In GTA IV, you will gain a police wanted level for any crime that you commit, providing there are witnesses present. The police can only chase you if they know where you are, and they need to see you to know where you are, so if you escape the search area marked on the radar without being spotted, your wanted level will disappear.
*The Police themselves have also been massively updated, they use AI to track you by sight. If they cannot see you, they will look for you until you are out of the Search Area. They behave more like real police and will respond to different crimes with different force. They will also work together, find cover and attempt to bring you down without harming innocent citizens.
* Liberty City's taxicabs provide an easy (and legal) way of travelling around the city. Inside the taxi, the camera changes to first-person mode. For convenience, you can "trip-skip" to the destination you choose.
Story & Missions
* The story and mission structure is different from previous GTA games, in that the story can be told in a number of different ways. Rockstar are trying to give people greater freedom and sense of control over their destiny. You now have a lot more choice in what you want to do.
* It is possible to do more than one mission at a time. For example, some missions take place over several days and may involve waiting for phone calls or attending interviews, and you are free to carry out other business during the waiting period.
Technology
* Grand Theft Auto 4 runs on Rockstar's proprietary next generation game engine, R.A.G.E., allowing for an unprecedented level of realism and interactivity.
* New sunlight and weather effects which give the city a whole different appearance as the time of day progresses.
* Volumetric lighting effects allow sunlight to stream realistically into dusty interiors. Police spotlights will likely benefit from this effect as well when helicopters kick up debris.
* Normal (bump) maps will provide much more detail in models than the underlying polygons, as well as giving materials more texture and depth.
* Road and building textures are more varied than in previous GTAs. On some roads you will find potholes, metal plates (etc) where the road has been dug up.
* Modern pixel shaders give water, glass, cars, etc.. more realistic reflections and shininess than the earlier games.
* In cars, you can see real reflections on the rear and side-view mirrors.
* There are no load times in GTA4, not even during exterior-interior transitions (and vice versa.)
* GTA4 uses euphoria, a fully procedural animation package created by NaturalMotion. Find out more about euphoria at the bottom of this page.
* Variations in the terrain are met with realistic changes in the walking animation.
* Characters will react realistically to being hit with gunfire, cars, and melee weapons or fists.
* Players will be able to push people out of the way, rather than "floating" past them as in older games.
* Falling/thrown characters will react as in real life- They won't simply be limp, lifeless ragdolls. Nor will they use a canned "super hero" animation like before.
* You will be able to hang on to helicopters and trucks, which will swing them around as the vehicle moves. However, you usually fall off after a short time.
Miscellaneous
* The camera angle behind the car is closer than it has been in previous GTAs. This allows you to see more detail on the cars, and more of the verticality of the city.
* In terms of scale, GTA IV is smaller than GTA: San Andreas, but the scale is much more accurate, since there is no desert or countryside in Liberty City. Liberty City in GTA4 is the biggest single city Rockstar have ever created.
More about euphoria...
To begin, NaturalMotion's euphoria engine is not a graphics engine. Several sources have claimed euphoria to be a graphics engine, which would power Grand Theft Auto IV. This is an incorrect statement. A graphics engine, commonly known as a game engine, is reponsible for creating real-time graphics for a game. NaturalMotion's euphoria engine is not so much concerned with rendering real-time graphics, as opposed to creating interactive animations for the game. The core technology is the Dynamic Motion Synthesis (DMS) system.
Provided enough processing power, such as in a next-generation console (PlayStation 3, Xbox 360), DMS is able to produce dynamic animations for in-game objects. One aspect of this, the DMS behaviors, simulates the responses of a human body to changes in its surroundings. This means that the animations you see taking place have not been pre-scripted or motion captured, as was the case in previous GTA games, but are generated on the fly. So for instance the same interaction with a pedestrian, repeated a dozen times, will produce a different outcome every time.
This technology is aimed to provide gamers with "unique game moments". Animations are created on the fly, so each player's experience will be unique. This brings Grand Theft Auto into a new world, since gamers are no longer subjected to pre-recorded animations; the game unfolds in a different way each time it is played.
This video showcases some of what the Euphoria engine is capable of:
http://www.youtube.com/watch?v=Ae3fgj2x1aI
