Vehicle rigging notes #

These are my own notes for rigging vehicles. Currently adapted to rigging trucks, as I've had to rig quite a few of these recently.

Documentation #

• Dimensions
• Total weight
• Weight per axle
• Engine specs and engine curve
• Transmission type, gears, gear ratios
• Axle ratio / Final ratio
• Top speed

Base rig #

Main GameObject + child mesh + child collider

Rigidbody: Total weight

VPVehicleController, VPTelemetry, VPStandardInput

WheelColliders

• Child WheelColliders GameObject with one VPWheelCollider child per wheel.
• Specify wheel meshes in VPWheelCollider.
• Context menu > Adjust position and radius to meshes. Verify alignment.
• Context menu > Configure Spring and Damper.
• Configure wheels in VPVehicleController > Axles

Center of Mass (CoM)

• Child GameObject, reference it in VPVehicleController > Center Of Mass
• Longitudinal position: use weight per axle from specifications.
• Preliminary: must be refined after configuring suspension.

Inertia

• Parametric. Configure dimensions.
• Leave 0 bias for now (configure based on handling afterwards).

Vehicle setup #

Driveline

• Differential: Final Ratio

Steering

• Max Steer Angle: Turn radius
• Ackerman: child GameObject approx. in the position of the rear axle. Reference it in VPVehicleController > Steering > Ackerman Reference

Brakes

• Trucks: ~12000, 0.6. Parking: ~15000, 0.5

Tires (Parametric Model)

Single truck wheels:

Adherent: 0.8
Peak: 1.6, 0.9
Limit: 8, 0.7
ABCD: 0.7, 0, 0.2, 0

Twin truck wheels (use VPTireFrictionModifier):

Adherent: 0,9
Peak: 1.8, 1.1
Limit: 8, 0.9
ABCD: 0.8, 0, 0.15, 0

Engine

• Engine curves and specs

Gearbox

• Gear ratios
• Gear up/down rpms, manual y automatic transmissions

Solver

• 12 substeps
• Trucks: Tire Impulse Ratio: 0.3-0.4
• Trucks: Engine Reaction Factor: 0.9

Effects

• Audio: add Truck Audio or Car Audio prefabs
• Visual effects

Suspension and dynamics #

Suspension

• Must support max weight per axle
• Traction trucks: test for max load over fifth wheel
• Anti-roll bars
• Progressive suspension (leaf springs, bumpers)
• Dynamic suspension (truck's pneumatic suspension)

Rolling Friction

• Coefficient: 0.005
• Factor of 2 for twin wheels

Aerodynamics

• European truck cabin: drag 3, downforce 0
• American truck cabin: drag 2.3, downforce 0.002
• Position: point where the average drag is generated

Center Of Mass

• Refine CoM position with the suspension working. Use the weight per axle from specifications

Safety aids #

ABS, ESC, ASR, TCS

Special vehicles #

Tandem + Trailer #

Usually the combined mass is specified. Use 55% for tandem, 45% for trailer.