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Simulation or arcade? This is the looming question that all developers of racing games face. A pure simulation model attempts to reproduce exactly what happens if you are driving a real vehicle. An arcade model is a fictional simulation of the driving experience. A pure imulation is desirable because it tends to feel very realistic and gives the player a solid connection to the vehicle and the environment. But being realistic, it is also very difficult to control. Not many people can drive a car 100 mph around a tight corner and live to see the next turn. A pure simulation tends to control the game design. An arcade-style simulation is relatively easy to control but bears little resemblance to reality and is in danger of disconnecting the player from the action. Being that there are no constraints for an arcade simulation, most racing games use this model. The arcade model can be shaped to fit any game design. The best solution lies somewhere between pure simulation and arcade. In this article, we will identify the components of the vehicle simulation that should be real and those that should be arcade, based on our experience working on RUMBLE RACING for Playstation 2.
Classification
The solution begins as it does for all software design, with classification. What are the major components of our vehicle simulation and how do they interact? A vehicle simulation can be broken up into five major modules: physics, collision, suspension, engine, and control (see Figure 1).
Physics. This module collects the forces applied at various points for a single frame of simulation and from these forces updates the vehicle's linear and angular velocities. These velocities are then used to update the position and orientation of the vehicle.
Collision. This module detects collisions of the vehicle body with the ground, walls, and objects. Once a collision is detected, the proper impulse force is applied to the physics module. These impulse forces are critical to both how real the simulation feels and how fun it is to play.
Suspension/wheels. The suspension module computes all forces generated by the suspension and the interaction of the tires with the ground. This is the trickiest module to write because the sources of force are numerous and complex.