protected override void LoadPhysics(Scene scene)
{
var wheelCenters = new[]
{
new Vector3(-10, -3, -15),
new Vector3(10, -3, -15),
new Vector3(-10, -3, 15),
new Vector3(10, -3, 15)
};
var wheels = new VehicleWheelsSimData(4);
var drive = new VehicleDriveSimData4W();
var chassis = new VehicleChassisData();
CreateVehicle4WSimulationData(1000, null, 3, null, wheelCenters, wheels, drive, chassis);
}
protected override void LoadPhysics(Scene scene)
{
var wheelCenters = new[]
{
new Vector3(-10, -3, -15),
new Vector3(10, -3, -15),
new Vector3(-10, -3, 15),
new Vector3(10, -3, 15)
};
var wheels = new VehicleWheelsSimData(4);
var drive = new VehicleDriveSimData4W();
var chassis = new VehicleChassisData();
CreateVehicle4WSimulationData(1000, null, 3, null, wheelCenters, wheels, drive, chassis);
}
private void CreateVehicle4WSimulationData(
float chassisMass,
ConvexMesh chassisConvexMesh,
float wheelMass,
ConvexMesh[] wheelConvexMeshes,
Vector3[] wheelCentreOffsets,
VehicleWheelsSimData wheelsData,
VehicleDriveSimData4W driveData,
VehicleChassisData chassisData)
{
const int TIRE_TYPE_SLICKS = 0;
//Extract the chassis AABB dimensions from the chassis convex mesh.
//Vector3 chassisDims = computeChassisAABBDimensions(chassisConvexMesh);
Vector3 chassisDims = new Vector3(10, 10, 10);
//The origin is at the center of the chassis mesh.
//Set the center of mass to be below this point and a little towards the front.
Vector3 chassisCMOffset = new Vector3(0.0f, -chassisDims.Y * 0.5f + 0.65f, 0.25f);
//Now compute the chassis mass and moment of inertia.
//Use the moment of inertia of a cuboid as an approximate value for the chassis moi.
Vector3 chassisMOI = new Vector3
(
(chassisDims.Y * chassisDims.Y + chassisDims.Z * chassisDims.Z) * chassisMass / 12.0f,
(chassisDims.X * chassisDims.X + chassisDims.Z * chassisDims.Z) * chassisMass / 12.0f,
(chassisDims.X * chassisDims.X + chassisDims.Y * chassisDims.Y) * chassisMass / 12.0f
);
//A bit of tweaking here. The car will have more responsive turning if we reduce the
//y-component of the chassis moment of inertia.
chassisMOI.Y *= 0.8f;
//Let's set up the chassis data structure now.
chassisData.Mass = chassisMass;
chassisData.MomentOfInertia = chassisMOI;
chassisData.CenterOfMassOffset = chassisCMOffset;
//Work out the front/rear mass split from the cm offset.
//This is a very approximate calculation with lots of assumptions.
//massRear*zRear + massFront*zFront = mass*cm (1)
//massRear + massFront = mass (2)
//Rearrange (2)
//massFront = mass - massRear (3)
//Substitute (3) into (1)
//massRear(zRear - zFront) + mass*zFront = mass*cm (4)
//Solve (4) for massRear
//massRear = mass(cm - zFront)/(zRear-zFront) (5)
//Now we also have
//zFront = (z-cm)/2 (6a)
//zRear = (-z-cm)/2 (6b)
//Substituting (6a-b) into (5) gives
//massRear = 0.5*mass*(z-3cm)/z (7)
float massRear = 0.5f * chassisMass * (chassisDims.Z - 3 * chassisCMOffset.Z) / chassisDims.Z;
float massFront = chassisMass - massRear;
//Extract the wheel radius and width from the wheel convex meshes.
float[] wheelWidths = new float[4];
float[] wheelRadii = new float[4];
//ComputeWheelWidthsAndRadii(wheelConvexMeshes, wheelWidths, wheelRadii);
wheelWidths = new[] { 3f, 3, 3, 3 };
wheelRadii = new[] { 1f, 1, 1, 1 };
//Now compute the wheel masses and inertias components around the axle's axis.
//http://en.wikipedia.org/wiki/List_of_moments_of_inertia
float[] wheelMOIs = new float[4];
for (int i = 0; i < 4; i++)
{
wheelMOIs[i] = 0.5f * wheelMass * wheelRadii[i] * wheelRadii[i];
}
//Let's set up the wheel data structures now with radius, mass, and moi.
VehicleWheelData[] wheels = new VehicleWheelData[4]
{
new VehicleWheelData(),
new VehicleWheelData(),
new VehicleWheelData(),
new VehicleWheelData()
};
for (int i = 0; i < 4; i++)
{
wheels[i].Radius = wheelRadii[i];
wheels[i].Mass = wheelMass;
wheels[i].MomentOfInertia = wheelMOIs[i];
wheels[i].Width = wheelWidths[i];
}
//Disable the handbrake from the front wheels and enable for the rear wheels
wheels[(int)VehicleWheelOrdering.FrontLeft].MaxHandBrakeTorque = 0.0f;
wheels[(int)VehicleWheelOrdering.FrontRight].MaxHandBrakeTorque = 0.0f;
wheels[(int)VehicleWheelOrdering.RearLeft].MaxHandBrakeTorque = 4000.0f;
wheels[(int)VehicleWheelOrdering.RearRight].MaxHandBrakeTorque = 4000.0f;
//Enable steering for the front wheels and disable for the front wheels.
wheels[(int)VehicleWheelOrdering.FrontLeft].MaxSteer = (float)System.Math.PI * 0.3333f;
wheels[(int)VehicleWheelOrdering.FrontRight].MaxSteer = (float)System.Math.PI * 0.3333f;
wheels[(int)VehicleWheelOrdering.RearLeft].MaxSteer = 0.0f;
wheels[(int)VehicleWheelOrdering.RearRight].MaxSteer = 0.0f;
//Let's set up the tire data structures now.
//Put slicks on the front tires and wets on the rear tires.
VehicleTireData[] tires = new VehicleTireData[4]
{
new VehicleTireData(),
new VehicleTireData(),
new VehicleTireData(),
new VehicleTireData()
};
tires[(int)VehicleWheelOrdering.FrontLeft].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.FrontRight].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.RearLeft].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.RearRight].Type = TIRE_TYPE_SLICKS;
//Let's set up the suspension data structures now.
VehicleSuspensionData[] susps = new VehicleSuspensionData[4]
{
new VehicleSuspensionData(),
new VehicleSuspensionData(),
new VehicleSuspensionData(),
new VehicleSuspensionData()
};
for (int i = 0; i < 4; i++)
{
susps[i].MaxCompression = 0.3f;
susps[i].MaxDroop = 0.1f;
susps[i].SpringStrength = 35000.0f;
susps[i].SpringDamperRate = 4500.0f;
}
susps[(int)VehicleWheelOrdering.FrontLeft].SprungMass = massFront * 0.5f;
susps[(int)VehicleWheelOrdering.FrontRight].SprungMass = massFront * 0.5f;
susps[(int)VehicleWheelOrdering.RearLeft].SprungMass = massRear * 0.5f;
susps[(int)VehicleWheelOrdering.RearRight].SprungMass = massRear * 0.5f;
//We need to set up geometry data for the suspension, wheels, and tires.
//We already know the wheel centers described as offsets from the rigid body centre of mass.
//From here we can approximate application points for the tire and suspension forces.
//Lets assume that the suspension travel directions are absolutely vertical.
//Also assume that we apply the tire and suspension forces 30cm below the centre of mass.
Vector3[] suspTravelDirections = new Vector3[] { new Vector3(0, -1, 0), new Vector3(0, -1, 0), new Vector3(0, -1, 0), new Vector3(0, -1, 0) };
Vector3[] wheelCentreCMOffsets = new Vector3[4];
Vector3[] suspForceAppCMOffsets = new Vector3[4];
Vector3[] tireForceAppCMOffsets = new Vector3[4];
for (int i = 0; i < 4; i++)
{
wheelCentreCMOffsets[i] = wheelCentreOffsets[i] - chassisCMOffset;
suspForceAppCMOffsets[i] = new Vector3(wheelCentreCMOffsets[i].X, -0.3f, wheelCentreCMOffsets[i].Z);
tireForceAppCMOffsets[i] = new Vector3(wheelCentreCMOffsets[i].X, -0.3f, wheelCentreCMOffsets[i].Z);
}
//Now add the wheel, tire and suspension data.
for (int i = 0; i < 4; i++)
{
wheelsData.SetWheelData(i, wheels[i]);
wheelsData.SetTireData(i, tires[i]);
wheelsData.SetSuspensionData(i, susps[i]);
wheelsData.SetSuspensionTravelDirection(i, suspTravelDirections[i]);
wheelsData.SetWheelCentreOffset(i, wheelCentreCMOffsets[i]);
wheelsData.SetSuspensionForceApplicationPointOffset(i, suspForceAppCMOffsets[i]);
wheelsData.SetTireForceApplicationPointOffset(i, tireForceAppCMOffsets[i]);
}
//Now set up the differential, engine, gears, clutch, and ackermann steering.
//Diff
VehicleDifferential4WData diff = new VehicleDifferential4WData();
diff.Type = VehicleDifferentialType.LimitedSlip4WheelDrive;
driveData.SetDifferentialData(diff);
//Engine
VehicleEngineData engine = new VehicleEngineData()
{
PeakTorque = 500.0f,
MaxOmega = 600.0f//approx 6000 rpm
};
driveData.SetEngineData(engine);
//Gears
VehicleGearsData gears = new VehicleGearsData()
{
SwitchTime = 0.5f
};
driveData.SetGearsData(gears);
//Clutch
VehicleClutchData clutch = new VehicleClutchData()
{
Strength = 10.0f
};
driveData.SetClutchData(clutch);
//Ackermann steer accuracy
var ackermann = new VehicleAckermannGeometryData()
{
Accuracy = 1.0f,
AxleSeparation = wheelCentreOffsets[(int)VehicleWheelOrdering.FrontLeft].Z - wheelCentreOffsets[(int)VehicleWheelOrdering.RearLeft].Z,
FrontWidth = wheelCentreOffsets[(int)VehicleWheelOrdering.FrontRight].X - wheelCentreOffsets[(int)VehicleWheelOrdering.FrontLeft].X,
RearWidth = wheelCentreOffsets[(int)VehicleWheelOrdering.RearRight].X - wheelCentreOffsets[(int)VehicleWheelOrdering.RearLeft].X
};
driveData.SetAckermannGeometryData(ackermann);
}
private void CreateVehicle4WSimulationData(
float chassisMass,
ConvexMesh chassisConvexMesh,
float wheelMass,
ConvexMesh[] wheelConvexMeshes,
Vector3[] wheelCentreOffsets,
VehicleWheelsSimData wheelsData,
VehicleDriveSimData4W driveData,
VehicleChassisData chassisData)
{
const int TIRE_TYPE_SLICKS = 0;
//Extract the chassis AABB dimensions from the chassis convex mesh.
//Vector3 chassisDims = computeChassisAABBDimensions(chassisConvexMesh);
Vector3 chassisDims = new Vector3(10, 10, 10);
//The origin is at the center of the chassis mesh.
//Set the center of mass to be below this point and a little towards the front.
Vector3 chassisCMOffset = new Vector3(0.0f, -chassisDims.Y * 0.5f + 0.65f, 0.25f);
//Now compute the chassis mass and moment of inertia.
//Use the moment of inertia of a cuboid as an approximate value for the chassis moi.
Vector3 chassisMOI = new Vector3
(
(chassisDims.Y * chassisDims.Y + chassisDims.Z * chassisDims.Z) * chassisMass / 12.0f,
(chassisDims.X * chassisDims.X + chassisDims.Z * chassisDims.Z) * chassisMass / 12.0f,
(chassisDims.X * chassisDims.X + chassisDims.Y * chassisDims.Y) * chassisMass / 12.0f
);
//A bit of tweaking here. The car will have more responsive turning if we reduce the
//y-component of the chassis moment of inertia.
chassisMOI.Y *= 0.8f;
//Let's set up the chassis data structure now.
chassisData.Mass = chassisMass;
chassisData.MomentOfInertia = chassisMOI;
chassisData.CenterOfMassOffset = chassisCMOffset;
//Work out the front/rear mass split from the cm offset.
//This is a very approximate calculation with lots of assumptions.
//massRear*zRear + massFront*zFront = mass*cm (1)
//massRear + massFront = mass (2)
//Rearrange (2)
//massFront = mass - massRear (3)
//Substitute (3) into (1)
//massRear(zRear - zFront) + mass*zFront = mass*cm (4)
//Solve (4) for massRear
//massRear = mass(cm - zFront)/(zRear-zFront) (5)
//Now we also have
//zFront = (z-cm)/2 (6a)
//zRear = (-z-cm)/2 (6b)
//Substituting (6a-b) into (5) gives
//massRear = 0.5*mass*(z-3cm)/z (7)
float massRear = 0.5f * chassisMass * (chassisDims.Z - 3 * chassisCMOffset.Z) / chassisDims.Z;
float massFront = chassisMass - massRear;
//Extract the wheel radius and width from the wheel convex meshes.
float[] wheelWidths = new float[4];
float[] wheelRadii = new float[4];
//ComputeWheelWidthsAndRadii(wheelConvexMeshes, wheelWidths, wheelRadii);
wheelWidths = new[] { 3f, 3, 3, 3 };
wheelRadii = new[] { 1f, 1, 1, 1 };
//Now compute the wheel masses and inertias components around the axle's axis.
//http://en.wikipedia.org/wiki/List_of_moments_of_inertia
float[] wheelMOIs = new float[4];
for (int i = 0; i < 4; i++)
{
wheelMOIs[i] = 0.5f * wheelMass * wheelRadii[i] * wheelRadii[i];
}
//Let's set up the wheel data structures now with radius, mass, and moi.
VehicleWheelData[] wheels = new VehicleWheelData[4]
{
new VehicleWheelData(),
new VehicleWheelData(),
new VehicleWheelData(),
new VehicleWheelData()
};
for (int i = 0; i < 4; i++)
{
wheels[i].Radius = wheelRadii[i];
wheels[i].Mass = wheelMass;
wheels[i].MomentOfInertia = wheelMOIs[i];
wheels[i].Width = wheelWidths[i];
}
//Disable the handbrake from the front wheels and enable for the rear wheels
wheels[(int)VehicleWheelOrdering.FrontLeftWheel].MaxHandBrakeTorque = 0.0f;
wheels[(int)VehicleWheelOrdering.FrontRightWheel].MaxHandBrakeTorque = 0.0f;
wheels[(int)VehicleWheelOrdering.RearLeftWheel].MaxHandBrakeTorque = 4000.0f;
wheels[(int)VehicleWheelOrdering.RearRightWheel].MaxHandBrakeTorque = 4000.0f;
//Enable steering for the front wheels and disable for the front wheels.
wheels[(int)VehicleWheelOrdering.FrontLeftWheel].MaxSteer = (float)System.Math.PI * 0.3333f;
wheels[(int)VehicleWheelOrdering.FrontRightWheel].MaxSteer = (float)System.Math.PI * 0.3333f;
wheels[(int)VehicleWheelOrdering.RearLeftWheel].MaxSteer = 0.0f;
wheels[(int)VehicleWheelOrdering.RearRightWheel].MaxSteer = 0.0f;
//Let's set up the tire data structures now.
//Put slicks on the front tires and wets on the rear tires.
VehicleTireData[] tires = new VehicleTireData[4]
{
new VehicleTireData(),
new VehicleTireData(),
new VehicleTireData(),
new VehicleTireData()
};
tires[(int)VehicleWheelOrdering.FrontLeftWheel].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.FrontRightWheel].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.RearLeftWheel].Type = TIRE_TYPE_SLICKS;
tires[(int)VehicleWheelOrdering.RearRightWheel].Type = TIRE_TYPE_SLICKS;
//Let's set up the suspension data structures now.
VehicleSuspensionData[] susps = new VehicleSuspensionData[4]
{
new VehicleSuspensionData(),
new VehicleSuspensionData(),
new VehicleSuspensionData(),
new VehicleSuspensionData()
};
for (int i = 0; i < 4; i++)
{
susps[i].MaxCompression = 0.3f;
susps[i].MaxDroop = 0.1f;
susps[i].SpringStrength = 35000.0f;
susps[i].SpringDamperRate = 4500.0f;
}
susps[(int)VehicleWheelOrdering.FrontLeftWheel].SprungMass = massFront * 0.5f;
susps[(int)VehicleWheelOrdering.FrontRightWheel].SprungMass = massFront * 0.5f;
susps[(int)VehicleWheelOrdering.RearLeftWheel].SprungMass = massRear * 0.5f;
susps[(int)VehicleWheelOrdering.RearRightWheel].SprungMass = massRear * 0.5f;
//We need to set up geometry data for the suspension, wheels, and tires.
//We already know the wheel centers described as offsets from the rigid body centre of mass.
//From here we can approximate application points for the tire and suspension forces.
//Lets assume that the suspension travel directions are absolutely vertical.
//Also assume that we apply the tire and suspension forces 30cm below the centre of mass.
Vector3[] suspTravelDirections = new Vector3[] { new Vector3(0, -1, 0), new Vector3(0, -1, 0), new Vector3(0, -1, 0), new Vector3(0, -1, 0) };
Vector3[] wheelCentreCMOffsets = new Vector3[4];
Vector3[] suspForceAppCMOffsets = new Vector3[4];
Vector3[] tireForceAppCMOffsets = new Vector3[4];
for (int i = 0; i < 4; i++)
{
wheelCentreCMOffsets[i] = wheelCentreOffsets[i] - chassisCMOffset;
suspForceAppCMOffsets[i] = new Vector3(wheelCentreCMOffsets[i].X, -0.3f, wheelCentreCMOffsets[i].Z);
tireForceAppCMOffsets[i] = new Vector3(wheelCentreCMOffsets[i].X, -0.3f, wheelCentreCMOffsets[i].Z);
}
//Now add the wheel, tire and suspension data.
for (int i = 0; i < 4; i++)
{
wheelsData.SetWheelData(i, wheels[i]);
wheelsData.SetTireData(i, tires[i]);
wheelsData.SetSuspensionData(i, susps[i]);
wheelsData.SetSuspensionTravelDirection(i, suspTravelDirections[i]);
wheelsData.SetWheelCentreOffset(i, wheelCentreCMOffsets[i]);
wheelsData.SetSuspensionForceApplicationPointOffset(i, suspForceAppCMOffsets[i]);
wheelsData.SetTireForceApplicationPointOffset(i, tireForceAppCMOffsets[i]);
}
//Now set up the differential, engine, gears, clutch, and ackermann steering.
//Diff
VehicleDifferential4WData diff = new VehicleDifferential4WData();
diff.Type = VehicleDifferentialType.LimitedSlip4WheelDrive;
driveData.SetDifferentialData(diff);
//Engine
VehicleEngineData engine = new VehicleEngineData()
{
PeakTorque = 500.0f,
MaxOmega = 600.0f //approx 6000 rpm
};
driveData.SetEngineData(engine);
//Gears
VehicleGearsData gears = new VehicleGearsData()
{
SwitchTime = 0.5f
};
driveData.SetGearsData(gears);
//Clutch
VehicleClutchData clutch = new VehicleClutchData()
{
Strength = 10.0f
};
driveData.SetClutchData(clutch);
//Ackermann steer accuracy
VehicleAckermannGeometryData ackermann = new VehicleAckermannGeometryData()
{
Accuracy = 1.0f,
AxleSeparation = wheelCentreOffsets[(int)VehicleWheelOrdering.FrontLeftWheel].Z - wheelCentreOffsets[(int)VehicleWheelOrdering.RearLeftWheel].Z,
FrontWidth = wheelCentreOffsets[(int)VehicleWheelOrdering.FrontRightWheel].X - wheelCentreOffsets[(int)VehicleWheelOrdering.FrontLeftWheel].X,
RearWidth = wheelCentreOffsets[(int)VehicleWheelOrdering.RearRightWheel].X - wheelCentreOffsets[(int)VehicleWheelOrdering.RearLeftWheel].X
};
driveData.SetAckermannGeometryData(ackermann);
}
