private static NewtonTire CreateTire(TireID tireID, TransformNode tireTrans,
GeometryNode carNode, float gravity)
{
NewtonTire tire = new NewtonTire();
Material tireMat = new Material();
tireMat.Diffuse = Color.Orange.ToVector4();
tireMat.Specular = Color.White.ToVector4();
tireMat.SpecularPower = 10;
float tireRadius = 1.4f;
GeometryNode tireNode = new GeometryNode("Race Car " + tireID + " Tire");
tireNode.Model = new Cylinder(tireRadius, tireRadius, 0.9f, 20);
tireNode.Material = tireMat;
carNode.AddChild(tireTrans);
tireTrans.AddChild(tireNode);
tire.Mass = 5.0f;
tire.Width = 0.3f * 1.25f;
tire.Radius = tireRadius;
switch (tireID)
{
case TireID.FrontLeft:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(-5.9f, 0, -3.0f));
break;
case TireID.FrontRight:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(-5.9f, 0, 3.0f));
break;
case TireID.RearLeft:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(5.0f, 0, -3.0f));
break;
case TireID.RearRight:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(5.0f, 0, 3.0f));
break;
}
// the tire will spin around the lateral axis of the same tire space
tire.Pin = Vector3.UnitZ;
tire.SuspensionLength = RaceCar.SUSPENSION_LENGTH;
float x = RaceCar.SUSPENSION_LENGTH;
tire.SuspensionSpring = (200.0f * (float)Math.Abs(gravity)) / x;
//tireSuspesionSpring = (100.0f * dAbs (GRAVITY)) / x;
float w = (float)Math.Sqrt(tire.SuspensionSpring);
// a critically damped suspension act too jumpy for a race car
tire.SuspensionShock = 1.0f * w;
// make it a little super critical y damped
//tireSuspesionShock = 2.0f * w;
tire.CollisionID = 0x100;
return(tire);
}
public RaceCar(Object container, NewtonPhysics engine) : base(container)
{
this.engine = engine;
//Crea los cuatro nodos de transformacion para las 4 Ruedas
tireTransNode = new TransformNode[4];
for (int i = 0; i < 4; i++)
{
tireTransNode[i] = new TransformNode();
}
// set the mass of the race car - Propiedad heredada
mass = VEHICLE_MASS;
// lower the center of the mass for a race car
centerOfMass = -Vector3.UnitY * 1.5f;
// sets up the callback function when body moves in the simulation
transformCallback = delegate(IntPtr body, float[] matrix)
{
Matrix mat = MatrixHelper.FloatsToMatrix(matrix);
// set the transformation of the vehicle body
PhysicsWorldTransform = mat;
Matrix invMat = Matrix.Invert(mat);
float[] tireMatrix = new float[16];
NewtonTire tire = null;
float sign = 0;
float angle = 0;
float brakePosition = 0;
// set the global matrix for each tire
for (IntPtr tyreId = Newton.NewtonVehicleGetFirstTireID(joint);
tyreId != IntPtr.Zero; tyreId = Newton.NewtonVehicleGetNextTireID(joint, tyreId))
{
int tireID = (int)GetTireID(tyreId);
tire = tires[tireID];
Newton.NewtonVehicleGetTireMatrix(joint, tyreId, tireMatrix);
// calculate the local matrix
Matrix tireMat = MatrixHelper.GetRotationMatrix(
MatrixHelper.FloatsToMatrix(tireMatrix) * invMat) * tire.TireOffsetMatrix;
tire.TireMatrix = tireMat;
tireTransNode[tireID].WorldTransformation = Matrix.CreateRotationX(MathHelper.PiOver2)
* tireMat;
// calcualte the parametric brake position
brakePosition = tireMat.Translation.Y - tire.TireRefHeight;
tire.BrakeMatrix = Matrix.CreateTranslation(0, tire.BrakeRefPosition.Y + brakePosition, 0);
// set suspensionMatrix
sign = (tire.BrakeRefPosition.Z > 0) ? 1 : -1;
angle = (float)Math.Atan2(sign * brakePosition, Math.Abs(tire.BrakeRefPosition.Z));
Matrix rotationMatrix = new Matrix(
1, 0, 0, 0,
0, (float)Math.Cos(angle), (float)Math.Sin(angle), 0,
0, -(float)Math.Sin(angle), (float)Math.Cos(angle), 0,
0, 0, 0, 1);
tire.AxelMatrix = rotationMatrix * tire.AxelMatrix;
tire.SuspensionTopMatrix = rotationMatrix * tire.SuspensionTopMatrix;
tire.SuspensionBottomMatrix = rotationMatrix * tire.SuspensionBottomMatrix;
}
};
forceCallback = delegate(IntPtr body)
{
float Ixx = 0, Iyy = 0, Izz = 0, tmpMass = 0;
Newton.NewtonBodyGetMassMatrix(body, ref tmpMass, ref Ixx, ref Iyy, ref Izz);
tmpMass *= (1.0f + (float)Math.Abs(GetSpeed()) / 20.0f);
float[] force = Vector3Helper.ToFloats(engine.GravityDirection * engine.Gravity * tmpMass);
Newton.NewtonBodySetForce(body, force);
};
tireUpdate = delegate(IntPtr vehicleJoint)
{
NewtonTire tire = null;
for (IntPtr tyreId = Newton.NewtonVehicleGetFirstTireID(vehicleJoint);
tyreId != IntPtr.Zero; tyreId = Newton.NewtonVehicleGetNextTireID(vehicleJoint, tyreId))
{
tire = tires[(int)GetTireID(tyreId)];
// If the tire is a front tire
if ((tire == tires[(int)TireID.FrontLeft]) || (tire == tires[(int)TireID.FrontRight]))
{
float currSteerAngle = Newton.NewtonVehicleGetTireSteerAngle(vehicleJoint, tyreId);
Newton.NewtonVehicleSetTireSteerAngle(vehicleJoint, tyreId,
currSteerAngle + (tire.Steer - currSteerAngle) * 0.035f);
}
else // if the tire is a rear tire
{
Newton.NewtonVehicleSetTireTorque(vehicleJoint, tyreId, tire.Torque);
if (tire.Brakes > 0)
{
// ask Newton for the precise acceleration needed to stop the tire
float brakeAcceleration =
Newton.NewtonVehicleTireCalculateMaxBrakeAcceleration(vehicleJoint, tyreId);
// tell Newton you want this tire stoped but only if the torque need it is less than
// the brakes pad can withstand (assume max brake pad torque is 500 newton * meter)
Newton.NewtonVehicleTireSetBrakeAcceleration(vehicleJoint, tyreId,
brakeAcceleration, 10000.0f);
// set some side slip as function of the linear speed
float speed = Newton.NewtonVehicleGetTireLongitudinalSpeed(vehicleJoint, tyreId);
Newton.NewtonVehicleSetTireMaxSideSleepSpeed(vehicleJoint, tyreId, speed * 0.1f);
}
}
}
};
bodyLeaveCallback = delegate(IntPtr body)
{
Respawn(body);
};
}
private static NewtonTire CreateTire(TireID tireID, TransformNode tireTrans,
GeometryNode carNode, float gravity)
{
NewtonTire tire = new NewtonTire();
Material tireMat = new Material();
tireMat.Diffuse = Color.Orange.ToVector4();
tireMat.Specular = Color.White.ToVector4();
tireMat.SpecularPower = 10;
float tireRadius = 0.7f;
GeometryNode tireNode = new GeometryNode("Race Car " + tireID + " Tire");
tireNode.Model = new Cylinder(tireRadius, tireRadius, 0.3f, 20);
tireNode.Material = tireMat;
carNode.AddChild(tireTrans);
tireTrans.AddChild(tireNode);
tire.Mass = 5.0f;
tire.Width = 0.3f * 1.25f;
tire.Radius = tireRadius;
switch (tireID)
{
case TireID.FrontLeft:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(-1.5f, 0, -1f));
break;
case TireID.FrontRight:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(-1.5f, 0, 1f));
break;
case TireID.RearLeft:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(1.5f, 0, -1f));
break;
case TireID.RearRight:
tire.TireOffsetMatrix = Matrix.CreateTranslation(new Vector3(1.5f, 0, 1f));
break;
}
// the tire will spin around the lateral axis of the same tire space
tire.Pin = Vector3.UnitZ;
tire.SuspensionLength = RaceCar.SUSPENSION_LENGTH;
// calculate the spring and damper contact for the subquestion
//
// from the equation of a simple spring the force is given by
// a = k * x
// where k is a spring constant and x is the displacement and a is the spring acceleration.
// we desire that a rest length the acceleration generated by the spring equal that of the gravity
// several gravity forces
// m * gravity = k * SUSPENSION_LENGTH * 0.5f,
float x = RaceCar.SUSPENSION_LENGTH;
tire.SuspensionSpring = (200.0f * (float)Math.Abs(gravity)) / x;
//tireSuspesionSpring = (100.0f * dAbs (GRAVITY)) / x;
// from the equation of a simple spring / damper system
// the system resonate at a frequency
// w^2 = ks
//
// and the damping attenuation is given by
// d = ks / 2.0f
// where:
// if d = w = 2 * pi * f -> the system is critically damped
// if d > w < 2 * pi * f -> the system is super critically damped
// if d < w < 2 * pi * f -> the system is under damped damped
// for a vehicle we usually want a suspension that is about 10% super critically damped
float w = (float)Math.Sqrt(tire.SuspensionSpring);
// a critically damped suspension act too jumpy for a race car
tire.SuspensionShock = 1.0f * w;
// make it a little super critical y damped
//tireSuspesionShock = 2.0f * w;
tire.CollisionID = 0x100;
return(tire);
}
