Blink 3D BlinkScript API

PhysicalWheel

The PhysicalWheel object is used in conjunction with the Entity object for physically modeling vehicles.

The PhysicsWheel.long??? and PhysicsWheel.lat??? properties are used to describe tire properties. Lateral and longitudal directions are calculated differently. They both take a measure for tire slip as input and produce a force or impulse as an output.

For people who are interested in the technical details the curve is a two piece cubic Hermite spline. Looking at the graph below, in the first part of the curve (0,0) to (extremumSlip, extremumValue), at which point the curve's tangent is zero. The second section goes from (extremumSlip, extremumValue) to (asymptoteSlip, asymptoteValue), at which point the curve's tangent is again zero.

Properties

type
  Usage String = PhysicalWheel.type
  Description Obtains the type of the object which is PhysicalWheel. (Read Only)
  Return Value Returns the type of the object as a string.
  Example

 
// Get the type of the object 
if ( PhysicalWheel.type == "PhysicalWheel" )
   Chat.print( "Object is of type PhysicalWheel" );
suspensionSpring
  Usage Entity = PhysicalWheel.suspensionSpring
  Description

Determines or sets the suspension spring coefficient. Essentially how springy is the suspension on the wheel.
  Return Value Returns the current suspension spring coefficient value.
  Example

 
// Set the springy ness of the suspension
oPhysicalWheel.suspensionSpring = 200;
suspensionDamper
  Usage Entity = PhysicalWheel.suspensionDamper
  Description

Determines or sets suspension damper coefficient. Essentially how quickly does the spring come to rest. The vehicle equivalent is the shock absorber. The value must be greater than or equal to 0.
  Return Value Returns the second entity involved in the collision or contact.
  Example

 
// Set the amount of damping applied to the suspension
oPhysicalWheel.suspensionDamper = 50;
suspensionTargetValue
  Usage Double = PhysicalWheel.suspensionTargetValue
  Description

Determines or sets the suspension target value (angle/position) of the suspension spring where the spring force is zero. Essentially the length of the spring when at rest along the distance specified in the PhysicalWheel.suspensionTravel property. Valid values range from 0 to 1. The default valu is 0.
  Return Value Returns the current target value for the suspension spring.
  Example

 
// Set the suspension target value
oPhysicalWheel.suspensionTargetValue = 100;
longExtremumSlip
  Usage Double = PhysicalWheel.longExtremumSlip
  Description

Determines or sets the extremal point of the curve. The value must be greater than or equal to 0. The defualt value is 1.0
  Return Value Returns the current longitudal extremum slip.
  Example

 
// Set the longitudal extremum slip
0PhysicalWheel.longExtremumSlip = 1.0;
latExtremumSlip
  Usage Double = PhysicalWheel.latExtremumSlip
  Description

Determines or sets the extremal point of the curve. The value must be greater than or equal to 0. The default value is 1.0
  Return Value Returns the current lateral extremum slip.
  Example

 
// Set the lateral extremum slip
0PhysicalWheel.latExtremumSlip = 1.0;
longExtemumValue
  Usage Double = PhysicalWheel.longExtremumValue
  Description

Determines or sets the extremal point of the curve. The value must be greater than or equal to 0. The defualt value is 0.02
  Return Value Returns the current longitudal extremum value.
  Example

 
// Set the longitudal extremum value
oPhysicalWheel.longExtremumValue = 0.02;
latExtemumValue
  Usage Double = PhysicalWheel.latExtremumValue
  Description

Determines or sets the extremal point of the curve. The value must be greater than or equal to 0. The defualt value is 0.02
  Return Value Returns the current lateral extremum value.
  Example

 
// Set the lateral extremum value
oPhysicalWheel.latExtremumValue = 0.02;
longAsymptoteSlip
  Usage Double = PhysicalWheel.longAsymptoteSlip
  Description

Determines or sets point on curve at which for all x > minumumX, function equals minimumY. The value must be greater than or equal to 0. The defualt value is 1.0.
  Return Value Returns the current longitudal asymptote slip.
  Example

 
// Set the lateral extremum value
oPhysicalWheel.longAsymptoteSlip = 1.0;
latAsymptoteSlip
  Usage Double = PhysicalWheel.latAsymptoteSlip
  Description

Determines or sets point on curve at which for all x > minumumX, function equals minimumY. The value must be greater than or equal to 0. The defualt value is 1.0.
  Return Value Returns the current lateral asymptote slip.
  Example

 
// Set the lateral extremum value
oPhysicalWheel.latAsymptoteSlip = 1.0;
longAsymptoteValue
  Usage Double = PhysicalWheel.longAsympoteValue
  Description

Determines or sets point on curve at which for all x > minumumX, function equals minimumY. The value must be greater than or equal to 0. The default value is 0.01.
  Return Value Returns the current longitudal asymptote value.
  Example

 
// Set the longitudal asymptote value
oPhysicalWheel.longAsymptoteValue = 0.01;
latAsymptoteValue
  Usage Double = PhysicalWheel.latAsympoteValue
  Description

Determines or sets point on curve at which for all x > minumumX, function equals minimumY. The value must be greater than or equal to 0. The default value is 0.01.
  Return Value Returns the current lateral asymptote value.
  Example

 
// Set the lateral asymptote value
oPhysicalWheel.latAsymptoteValue = 0.01;
longStiffnessFactor
  Usage Vector = PhysicalWheel.longStiffnessFactor
  Description

Determines or sets the scaling factor for tire force. An additional overall positive scaling that is applied to tire forces before they are passed to the solver. Higher values make improve grip. Increasing the PhysicsWheel.longExtremumValue property may require that this property's value be lowered. Setting this property to 0 zero will disable all longitudal friction. The default value is 1000000.0

  Return Value Returns the normal impulse of the contact or collision.
  Example

 
// Set the stiffnessfactor
oPhysicalWheel.longStifnessFactor = 500000.0;
latStiffnessFactor
  Usage Vector = PhysicalWheel.latStiffnessFactor
  Description

Determines or sets the scaling factor for tire force. An additional overall positive scaling that is applied to tire forces before they are passed to the solver. Higher values make improve grip. Increasing the PhysicsWheel.latExtremumValue property may require that this properties value be lowered. Setting this property to 0 zero will disable all lateral friction. The default value is 1000000.0

  Return Value Returns the normal impulse of the contact or collision.
  Example

 
// Set the stiffness factor
oPhysicalWheel.latStifnessFactor = 500000.0;
longInputSlipVelocity
  Usage Double = PhysicalWheel.longInputSlipVelocity
  Description

Enables or disables using the longitudinal slip velocity as input for the tire properties, rather than the slip angle. When set to true the longitudinal slip velocity is used.
  Return Value Returns true if the longitudinal slip velocity is used as input to the tire properties.
  Example

 
// Use longitudal slip velocity as input to tire properties
PhysicalWheel.longInputSlipVelocity;
latInputSlipVelocity
  Usage Boolean = PhysicalWheel.latInputSlipVelocity
  Description

Enables or disables using the lateral slip velocity as input to the tire properties, rather than the slip angle. When set to true the lateral slip velocity is used.
  Return Value Returns true if the lateral slip velocity is used as input to the tire properties.
  Example

 
// Use lateral slip velocity as input to tire properties
PhysicalWheel.longInputSlipVelocity;
axisContactNormal
  Usage Boolean = PhysicalWheel.axisContactNormal
  Description

Determines if the suspension axis or the ground contact normal is used for the suspension constraint. When set to true the ground contact normal is used. The default value is false.
  Return Value Returns true if the ground contact normal is being used for the suspension constraint
  Example

 
// Use the ground contact normal for the suspension constraint
oPhysicalWheel.axisContactNormal = true;
unscaledSpringBehavior
  Usage Boolean = PhysicalWheel.unscaledSpringbehavior
  Description

Determines how suspension travel and wheel radius from the suspension spring is handled. When set to true, the system does not factor out the suspension travel and wheel radius from the spring force computation.
  Return Value Returns true if the system should not factor out suspendion travel and wheel radius from the spring force computaton..
  Example

 
// Stop the system from factoring in suspension travel etc.
oPhysicalWheel.unscaledSpringBehavior = true;
axleSpeedOverride
  Usage Boolean = PhysicalWheel.axleSpeedOverride
  Description Enables or disables axle speed override. If set to true, the axle speed is not computed by the simulation. It should therefore be specified directly every frame using the PhysicalModel.axleSpeed property.
  Return Value Returns true if axle speed override is enabled.
  Example

 
// Set the axle speed
oEntity.physicalModel.axleSpeedOverride = true;

this.oTimestep1 = new Object();
this.oTimestep1.oEntity = oEntity;
this.oTimestep1.timestep = function( dElapsedTime, dDeltaTime )
{
  this.oEntity.physicalWheel.axleSpeed = 500;
}
suspensionTravel
  Usage Double = PhysicalWheel.suspensionTravel
  Description Determines or sets the maximum extension distance of suspension along the Entity's -Y axis. Essentially what is the longest the suspension spring can be stretched to. Valid values 0 to infinite.
  Return Value Returns the current length of suspension travel.
  Example

 
// Set the length of suspension travel
oPhysicalWheel.suspensionTravel = 50;
inverseWheelMass
  Usage Double = PhysicalWheel.inverseWheelMass
  Description Determines or sets the inverse mass of the wheel which determines the wheel velocity that wheel torques can achieve. The default value is 1.0, values must be greater than or equal to 0.
  Return Value Returns the current inverse wheel mass.
  Example

 
// Set the inverse wheel mass
oPhysicalWheel.inverseWheelMass = 2.0;
motorTorque
  Usage Double = PhysicalWheel.motorTorque
  Description Determines or sets the engine torque on the wheel axle. Use positive values to move forward and negative values to reverse. This property will have no effect if PhysicalMaterial.axleSpeedOverride is set to true.
  Return Value Returns the current engine torque.
  Example

 
// Set the engine torque
oPhysicalWheel.motorTorque = 500;
brakeTorque
  Usage Double = PhysicalWheel.brakeTorque
  Description Determines or sets the brake torque. Increasing the value of this property is the equivalent of applying the brakes in a car. Values must be greater than or equal to 0. Very large values will lock wheel. This property will have no effect if PhysicalMaterial.axleSpeedOverride is set to true.

 
  Return Value Returns the current brake torque.
  Example

 
// Set the brake torque
oPhysicalWheel.brakeTorque = 10;
steerAngle
  Usage Double = PhysicalWheel.steerAngle
  Description Determines or sets the steering angle, around Entity's Y axis. Valid values are -PI to PI.
  Return Value Returns the current steer angle around the Entity's Y axis.
  Example

 
// Set the steer angle
oPhysicalWheel.steerAngle = 0.5;
axleSpeed
  Usage Double = PhysicalWheel.axleSpeed
  Description

Determines or sets the current axle rotation speed. This property only has an effect if the PhysicalWheel.axleSpeedOverride property is set to true. If the PhysicalWheel.axleSpeedOverride property is set to true the PhysicalWheel.motorTorque and PhysicalWheel.brakeTorques properties are ineffective. This property must be set for every frame. Values can be positive or negative depending on the direction of rotation.

  Return Value Returns the current axle speed.
  Example

 
// Set the axle speed
oEntity.physicalModel.axleSpeedOverride = true;

this.oTimestep1 = new Object();
this.oTimestep1.oEntity = oEntity;
this.oTimestep1.timestep = function( dElapsedTime, dDeltaTime )
{
  this.oEntity.physicalWheel.axleSpeed = 500;
}

 

 
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