Model Proportions in GTA 3 & Vice City Handling

Imagine your car is simply being the wheel dummies. These are all your model basically is when concerning the handling file. Making a model very narrow between the wheels (the track of the car) it will be much easier to roll than having a very wide track. Just like a Diablo is harder to roll than a Mini - both have similar centres of mass on the Z axis measure from the ground up, but the difference in track makes the mini roll more in corners.

Making the distance between the front and rear wheels very far (the wheelbase of the car) will make the car very stable in a straight line but it will be much harder to turn. This is best demonstrated by a Top-fuel Dragster with some 6000bhp and is around 10m metres long. Compare this to a Lancia Stratos, which around 200bhp and is about 4m long. The Lancia is not as stable at high speeds as the dragster, despite the Lancia having much less power. The shorter wheelbase of the Lancia allows the car to turn better than the dragster, even thought dragster has far larger tyres.

If you got the track and wheelbase right then the car would begin to inherantly handle more like the real thing simply though virtue of these principals. You can even do experiments to discover the precise effect of model proportions.

A Possible Experiment

Make four simple cars to the dimensions shown in the below table. The shape of the car bodies does not matter, this experiment just concentrates on their wheel positions.

The dimensions I would suggest are here:

Track Wheelbase
A 1 5
B 2 5
C 5 2
D 5 1

Set their handling to be indentical to each other and drive them around in the game. You will find that:

  1. Very stable in a straight line but is hard to turn.
  2. Less stable in a straight line and is more agile than A is.
  3. Unstable in a straight line but are much more agile than A or B are.
  4. More stable than C is.

Thus it is proved that the proportions of vehicle models has a direct impact on how the vehicle will handle. If you are feeling adventurous you could make some other test vehicles with their front track wider than the rear and vice versa to see how the game reacts to those.

So What?

From further experimentation you will find that a car with a track of around 1.8m to 2.0m and a wheelbase of around 4.0m to 4.5m will be the best comprimise for the twisty nature of city steets. Unsuprisingly, these are the dimensions that all modern race cars are derived from - proof that getting the size of your models right is crucial even in a computer game.

With the model correctly proportioned, the handling can be made more realistic than with a badly proportioned vehicle. Ignoring the track and wheelbase means the model will be using the fundamental agility from a completely different car.