FAQ / How To

I'd better name this section "FAQ / OAC", including the Once Asked Questions. When I receive a question that requires a detailed answer, I post it here as well so there's no need for asking / answering the same question again :)

How to configure the Input parameters

I recommend to use these settings for Horizontal and Vertical axes:

Edy's Vehicle Physics input axes

How to control the vehicle from scripting

Write a custom input script that gets a reference to the VehicleController component, then modify its input properties as you wish: steerInput, throttleInput, brakeInput and handBrakeInput.

You can check out the scripts VehicleStandardInput.cs and VehicleRandomInput.cs script as examples on how to control the vehicle with custom code.

How to create vehicles at runtime

The order of events for creating vehicles at runtime is:

  1. Create the root GameObject and disable it (GameObject.SetActive(false))
  2. Build the hierarchy with child GameObjects and components
  3. Configure all the components and references. In particular, ensure that the wheels list in the VehicleController component is populated properly.
  4. Enable the root GameObject (GameObject.SetActive(true))

These properties cannot change while VehicleController is enabled

Arcade cars: quicker turns, minimal sliding

These settings at the Vehicle Controller component turn most vehicles into arcade vehicles a'la Mario Kart or Outrun:

How to configure a car for drifting

A prefab Sport Coupe Drift is included. The key settings for configuring the drifting behavior are:

How to match real-world cars

You can configure the vehicles in EVP to resemble the feeling and behavior of actual cars, but not to perform an accurate simulation of a specific car. The parameters in EVP are designed for configuring the vehicle behavior easily and don't have a correspondence with the real world's settings.

A good method is starting with one of the included prefabs. Choose the one that is most similar to the vehicle you want to resemble. Then carefully configure its parameters in order to fine tune the handling and behavior.

If you need to match the specifications of real cars accurately then take a look at Vehicle Physics Pro. VPP is specifically designed to use real-world specifications and simulate the actual behaviors of the cars based on their realistic setup.

Some hints:

Suspension and height of the center of mass
Set stiffer suspension, shorter suspension distances, and lower center of mass for sports cars. Softer suspension, larger suspension distances, and higher center of mass for family cars / pickup trucks.
Engine force and shape
More Max Drive Force and higher Force Curve Shape for high-acceleration sports cars. Less drive force and lower curve shapes for regular street cars.
Max Speed Forward, Aerodynamic Drag
The combination of these define the final top speed on flat road.
Vehicle Balance
These settings define how the parameters are balanced among front and rear wheels. They may be used for compensating or enforcing certain behaviors on specific situations (example: move the brake balance to the rear wheels for enforcing over-steer on braking).
Position of the Center of Mass
The longitudinal position of the center of mass has great influence on the handling and behavior as well. A good practice is to ensure the suspension to be properly configured according to the weight distribution as for the the CoM position (i.e. stiffer springs where more weight is supported).

Which parameter(s) affect each vehicle aspect?

Most parameters affect each aspect in some way, but here is an useful guide:

Top speed
  • Max Speed Forward
  • Aerodynamic Drag
  • Ground Material's Drag
Steering
  • Max Steer Angle
  • Steering Limit reduces the angle with the speed
  • Steering Assist automatically counter-steers for keeping the control
  • Handling Bias tweaks the understeer / oversteer behavior
Acceleration
  • Max Drive Force
  • Force Curve Shape
  • Aerodynamic Drag
  • Ground Material's Drag
  • Tire Friction transmits up to Max Drive Force to the wheels
  • Aided by Traction Control
Burnouts / Drifting / Powersliding
  • Max Drive Force
  • Max Drive Slip
  • Drive Force To Max Slip
  • Drive Balance configures the drive wheels
  • Tire Friction transmits up to Max Drive Force to the wheels
  • Traction Control should be disabled or with small value
Brake power
  • Max Brake Force
  • Tire Friction (Max Brake Force to the wheels)
  • Aided by Brake Assist
  • Balanced by Brake Balance
Brake locks
  • Max Brake Slip or Max Brake Ratio
  • Brake Force To Max Slip
  • Brake Balance
  • Brake Assist should be disabled or with small value
Handling
  • All parameters in "Vehicle Balance"
  • All parameters in "Driving Aids"
  • Anti-roll
  • Max Drive Slip
  • Drive Force To Max Slip
  • Center of Mass (Position and Height)
Weight Transfer
  • Suspension dampers
  • Anti-roll
  • Height of Center of Mass
Car stopping distance with no user input applied
  • Rolling Resistance
  • Aerodynamic Drag (very small effect)
  • Ground Material's Drag

How to configure the driver's first person view

Create a GameObject in the vehicle at the approximate position of the first person view.

Add these components:

Configurable Joint for the driver's first person view

Problem resolution

The car jumps uncontrollably or shakes at rest

Watch the damper values at the WheelColliders and/or the mass of the vehicle rigidbody.

Impacts cause a noticeable lag

Remove the colliders from the Deform Colliders list. Deforming the colliders is an expensive operation as the convex hulls are recomputed.

Scaled vehicles don't work correctly

Scaling vehicles can cause unpredictable issues due to how physics are handled in Unity. Thus, scales other than 1 in the Rigidbody and WheelColliders (including their parent GameObjects) are not supported and are indeed strongly discouraged.

You may scale the mesh GameObjects only. As long as the Rigidbody and the WheelColliders receive a final scale of 1, then the vehicles will work as expected. If you scale the meshes, then you should modify the WheelColliders to accommodate the new positions and wheel dimensions (radius, suspension length).