/// <summary>
/// Constructs a new constraint which restricts three degrees of linear freedom and one degree of angular freedom between two entities.
/// </summary>
/// <param name="connectionA">First entity of the constraint pair.</param>
/// <param name="connectionB">Second entity of the constraint pair.</param>
/// <param name="anchor">Point around which both entities rotate.</param>
/// <param name="hingeAxis">Axis of allowed rotation in world space to be attached to connectionA. Will be kept perpendicular with the twist axis.</param>
public SwivelHingeJoint(Entity connectionA, Entity connectionB, ref Vector3 anchor, ref Vector3 hingeAxis)
{
if (connectionA == null)
connectionA = TwoEntityConstraint.WorldEntity;
if (connectionB == null)
connectionB = TwoEntityConstraint.WorldEntity;
BallSocketJoint = new BallSocketJoint(connectionA, connectionB, ref anchor);
Vector3 tmp;
BallSocketJoint.OffsetB.Invert( out tmp );
AngularJoint = new SwivelHingeAngularJoint(connectionA, connectionB, ref hingeAxis, ref tmp );
HingeLimit = new RevoluteLimit(connectionA, connectionB);
HingeMotor = new RevoluteMotor(connectionA, connectionB, hingeAxis);
TwistLimit = new TwistLimit(connectionA, connectionB, ref BallSocketJoint.worldOffsetA, ref tmp, 0, 0);
TwistMotor = new TwistMotor(connectionA, connectionB, ref BallSocketJoint.worldOffsetA, ref tmp );
HingeLimit.IsActive = false;
HingeMotor.IsActive = false;
TwistLimit.IsActive = false;
TwistMotor.IsActive = false;
//Ensure that the base and test direction is perpendicular to the free axis.
Vector3 baseAxis; anchor.Sub( ref connectionA.position, out baseAxis );
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon) //anchor and connection a in same spot, so try the other way.
connectionB.position.Sub( ref anchor, out baseAxis );
baseAxis.AddScaled( ref hingeAxis, -Vector3.Dot( ref baseAxis, ref hingeAxis) , out baseAxis );
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
//However, if the free axis is totally aligned (like in an axis constraint), pick another reasonable direction.
Vector3.Cross(ref hingeAxis, ref Vector3.Up, out baseAxis);
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
Vector3.Cross(ref hingeAxis, ref Vector3.Right, out baseAxis);
}
}
HingeLimit.Basis.SetWorldAxes(ref hingeAxis, ref baseAxis, ref connectionA.orientationMatrix);
HingeMotor.Basis.SetWorldAxes( ref hingeAxis, ref baseAxis, ref connectionA.orientationMatrix);
connectionB.position.Sub( ref anchor, out baseAxis );
baseAxis.AddScaled( ref hingeAxis, -Vector3.Dot(ref baseAxis, ref hingeAxis), out baseAxis );
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
//However, if the free axis is totally aligned (like in an axis constraint), pick another reasonable direction.
Vector3.Cross(ref hingeAxis, ref Vector3.Up, out baseAxis);
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
Vector3.Cross(ref hingeAxis, ref Vector3.Right, out baseAxis);
}
}
HingeLimit.TestAxis = baseAxis;
HingeMotor.TestAxis = baseAxis;
Add(BallSocketJoint);
Add(AngularJoint);
Add(HingeLimit);
Add(HingeMotor);
Add(TwistLimit);
Add(TwistMotor);
}
/// <summary>
/// Constructs a new constraint which restricts three degrees of linear freedom and one degree of angular freedom between two entities.
/// </summary>
/// <param name="connectionA">First entity of the constraint pair.</param>
/// <param name="connectionB">Second entity of the constraint pair.</param>
/// <param name="anchor">Point around which both entities rotate.</param>
/// <param name="hingeAxis">Axis of allowed rotation in world space to be attached to connectionA. Will be kept perpendicular with the twist axis.</param>
public SwivelHingeJoint(Entity connectionA, Entity connectionB, Vector3 anchor, Vector3 hingeAxis)
{
if (connectionA == null)
connectionA = TwoEntityConstraint.WorldEntity;
if (connectionB == null)
connectionB = TwoEntityConstraint.WorldEntity;
BallSocketJoint = new BallSocketJoint(connectionA, connectionB, anchor);
AngularJoint = new SwivelHingeAngularJoint(connectionA, connectionB, hingeAxis, -BallSocketJoint.OffsetB);
HingeLimit = new RevoluteLimit(connectionA, connectionB);
HingeMotor = new RevoluteMotor(connectionA, connectionB, hingeAxis);
TwistLimit = new TwistLimit(connectionA, connectionB, BallSocketJoint.OffsetA, -BallSocketJoint.OffsetB, 0, 0);
TwistMotor = new TwistMotor(connectionA, connectionB, BallSocketJoint.OffsetA, -BallSocketJoint.OffsetB);
HingeLimit.IsActive = false;
HingeMotor.IsActive = false;
TwistLimit.IsActive = false;
TwistMotor.IsActive = false;
//Ensure that the base and test direction is perpendicular to the free axis.
Vector3 baseAxis = anchor - connectionA.position;
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon) //anchor and connection a in same spot, so try the other way.
baseAxis = connectionB.position - anchor;
baseAxis -= Vector3.Dot(baseAxis, hingeAxis) * hingeAxis;
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
//However, if the free axis is totally aligned (like in an axis constraint), pick another reasonable direction.
baseAxis = Vector3.Cross(hingeAxis, Vector3.Up);
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
baseAxis = Vector3.Cross(hingeAxis, Vector3.Right);
}
}
HingeLimit.Basis.SetWorldAxes(hingeAxis, baseAxis, connectionA.orientationMatrix);
HingeMotor.Basis.SetWorldAxes(hingeAxis, baseAxis, connectionA.orientationMatrix);
baseAxis = connectionB.position - anchor;
baseAxis -= Vector3.Dot(baseAxis, hingeAxis) * hingeAxis;
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
//However, if the free axis is totally aligned (like in an axis constraint), pick another reasonable direction.
baseAxis = Vector3.Cross(hingeAxis, Vector3.Up);
if (baseAxis.LengthSquared() < Toolbox.BigEpsilon)
{
baseAxis = Vector3.Cross(hingeAxis, Vector3.Right);
}
}
HingeLimit.TestAxis = baseAxis;
HingeMotor.TestAxis = baseAxis;
Add(BallSocketJoint);
Add(AngularJoint);
Add(HingeLimit);
Add(HingeMotor);
Add(TwistLimit);
Add(TwistMotor);
}
/// <summary>
/// Constructs a new constraint which restricts three degrees of linear freedom and one degree of angular freedom between two entities.
/// This constructs the internal constraints, but does not configure them. Before using a constraint constructed in this manner,
/// ensure that its active constituent constraints are properly configured. The entire group as well as all internal constraints are initially inactive (IsActive = false).
/// </summary>
public SwivelHingeJoint()
{
IsActive = false;
BallSocketJoint = new BallSocketJoint();
AngularJoint = new SwivelHingeAngularJoint();
HingeLimit = new RevoluteLimit();
HingeMotor = new RevoluteMotor();
TwistLimit = new TwistLimit();
TwistMotor = new TwistMotor();
Add(BallSocketJoint);
Add(AngularJoint);
Add(HingeLimit);
Add(HingeMotor);
Add(TwistLimit);
Add(TwistMotor);
}
/// <summary>
/// Constructs a new demo.
/// </summary>
/// <param name="game">Game owning this demo.</param>
public ReverseTrikeDemo(DemosGame game)
: base(game)
{
game.Camera.Position = new Vector3(0, 2, 15);
Space.Add(new Box(new Vector3(0, -5, 0), 20, 1, 20));
var body = new Box(new Vector3(0, 0, 0), 2, 1, 3, 10);
body.CollisionInformation.LocalPosition = new Vector3(0, .8f, 0);
Space.Add(body);
#region First Wheel
var wheel = new Cylinder(body.Position + new Vector3(-1.3f, 0, -1.5f), .2f, .5f, 4);
wheel.Material = new Material(1.5f, 1.5f, 0);
wheel.Orientation = Quaternion.CreateFromAxisAngle(Vector3.Forward, MathHelper.PiOver2);
//Preventing the occasional pointless collision pair can speed things up.
CollisionRules.AddRule(body, wheel, CollisionRule.NoBroadPhase);
//Connect the wheel to the body.
var ballSocketJoint = new BallSocketJoint(body, wheel, wheel.Position);
var swivelHingeAngularJoint = new SwivelHingeAngularJoint(body, wheel, Vector3.Up, Vector3.Right);
//Motorize the wheel.
drivingMotor1 = new RevoluteMotor(body, wheel, Vector3.Left);
drivingMotor1.Settings.VelocityMotor.Softness = .2f;
//Let it roll when the user isn't giving specific commands.
drivingMotor1.IsActive = false;
steeringMotor1 = new RevoluteMotor(body, wheel, Vector3.Up);
steeringMotor1.Settings.Mode = MotorMode.Servomechanism;
//The constructor makes a guess about how to set up the constraint.
//It can't always be right since it doesn't have all the information;
//in this case, it chooses the basis and test axis incorrectly.
//This leads to a 'flipping' behavior when the wheel is rolling
//(the test axis is 'rolling' with the wheel, and passes over
//a singularity which causes a flip).
//To fix this, we configure the constraint directly.
//The basis is aligned with how the wheel is set up; we choose 'up' as
//the motorized axis, and right/forward to define the angle measurement plane.
//The test axis is set to be perpendicular to the wheel's rotation so that
//it only measures the steering angle.
//If you're curious, the angle measurement is just a Math.Atan2.
//The current world test axis is dotted against the two plane axes (Right and Forward here).
//This gives an x and y value. These can be plugged into Atan2 just like when
//you compute an angle on a normal 2d graph.
steeringMotor1.Basis.SetWorldAxes(Vector3.Up, Vector3.Right);
steeringMotor1.TestAxis = Vector3.Right;
//Add the wheel and connection to the space.
Space.Add(wheel);
Space.Add(ballSocketJoint);
Space.Add(swivelHingeAngularJoint);
Space.Add(drivingMotor1);
Space.Add(steeringMotor1);
#endregion
#region Second Wheel
wheel = new Cylinder(body.Position + new Vector3(1.3f, 0, -1.5f), .2f, .5f, 4);
wheel.Material = new Material(1.5f, 1.5f, 0);
wheel.Orientation = Quaternion.CreateFromAxisAngle(Vector3.Forward, MathHelper.PiOver2);
//Preventing the occasional pointless collision pair can speed things up.
CollisionRules.AddRule(body, wheel, CollisionRule.NoBroadPhase);
//Connect the wheel to the body.
ballSocketJoint = new BallSocketJoint(body, wheel, wheel.Position);
swivelHingeAngularJoint = new SwivelHingeAngularJoint(body, wheel, Vector3.Up, Vector3.Right);
//Motorize the wheel.
drivingMotor2 = new RevoluteMotor(body, wheel, Vector3.Left);
drivingMotor2.Settings.VelocityMotor.Softness = .2f;
//Let it roll when the user isn't giving specific commands.
drivingMotor2.IsActive = false;
steeringMotor2 = new RevoluteMotor(body, wheel, Vector3.Up);
steeringMotor2.Settings.Mode = MotorMode.Servomechanism;
//Configure the motor. See wheel 1 for more description.
steeringMotor2.Basis.SetWorldAxes(Vector3.Up, Vector3.Right);
steeringMotor2.TestAxis = Vector3.Right;
//Add the wheel and connection to the space.
Space.Add(wheel);
Space.Add(ballSocketJoint);
Space.Add(swivelHingeAngularJoint);
Space.Add(drivingMotor2);
Space.Add(steeringMotor2);
#endregion
#region Third Wheel
wheel = new Cylinder(body.Position + new Vector3(0, -.3f, 1.5f), .2f, .5f, 4);
wheel.Material = new Material(1.5f, 1.5f, 0);
wheel.Orientation = Quaternion.CreateFromAxisAngle(Vector3.Forward, MathHelper.PiOver2);
//Preventing the occasional pointless collision pair can speed things up.
CollisionRules.AddRule(body, wheel, CollisionRule.NoBroadPhase);
//Connect the wheel to the body.
ballSocketJoint = new BallSocketJoint(body, wheel, wheel.Position);
//Notice that the third wheel isn't a swivel hinge, it's just a revolute axis.
//This lets it roll, but prevents flopping around like the wheels of a grocery cart.
//Could have used a RevoluteJoint solver group here, but this shows it's possible to do
//the same things without using the combo-constraints.
var revoluteAngularJoint = new RevoluteAngularJoint(body, wheel, Vector3.Right);
//Add the wheel and connection to the space.
Space.Add(wheel);
Space.Add(ballSocketJoint);
Space.Add(revoluteAngularJoint);
#endregion
int xLength = 180;
int zLength = 180;
float xSpacing = 8f;
float zSpacing = 8f;
var heights = new float[xLength, zLength];
for (int i = 0; i < xLength; i++)
{
for (int j = 0; j < zLength; j++)
{
float x = i - xLength / 2;
float z = j - zLength / 2;
//heights[i,j] = (float)(x * y / 1000f);
heights[i, j] = (float)(10 * (Math.Sin(x / 8) + Math.Sin(z / 8)));
//heights[i,j] = 3 * (float)Math.Sin(x * y / 100f);
//heights[i,j] = (x * x * x * y - y * y * y * x) / 1000f;
}
}
//Create the terrain.
var terrain = new Terrain(heights, new AffineTransform(
new Vector3(xSpacing, 1, zSpacing),
Quaternion.Identity,
new Vector3(-xLength * xSpacing / 2, -10, -zLength * zSpacing / 2)));
Space.Add(terrain);
game.ModelDrawer.Add(terrain);
}
Entity AddDriveWheel(Vector3 wheelOffset, Entity body, out RevoluteMotor drivingMotor, out RevoluteMotor steeringMotor)
{
var wheel = new Cylinder(body.Position + wheelOffset, .4f, .5f, 5f);
wheel.Material.KineticFriction = 2.5f;
wheel.Material.StaticFriction = 3.5f;
wheel.Orientation = Quaternion.CreateFromAxisAngle(Vector3.Forward, MathHelper.PiOver2);
//Preventing the occasional pointless collision pair can speed things up.
CollisionRules.AddRule(wheel, body, CollisionRule.NoBroadPhase);
//Connect the wheel to the body.
var pointOnLineJoint = new PointOnLineJoint(body, wheel, wheel.Position, Vector3.Down, wheel.Position);
var suspensionLimit = new LinearAxisLimit(body, wheel, wheel.Position, wheel.Position, Vector3.Down, -1, 0);
//This linear axis motor will give the suspension its springiness by pushing the wheels outward.
var suspensionSpring = new LinearAxisMotor(body, wheel, wheel.Position, wheel.Position, Vector3.Down);
suspensionSpring.Settings.Mode = MotorMode.Servomechanism;
suspensionSpring.Settings.Servo.Goal = 0;
suspensionSpring.Settings.Servo.SpringSettings.Stiffness = 300;
suspensionSpring.Settings.Servo.SpringSettings.Damping = 70;
var swivelHingeAngularJoint = new SwivelHingeAngularJoint(body, wheel, Vector3.Up, Vector3.Right);
//Motorize the wheel.
drivingMotor = new RevoluteMotor(body, wheel, Vector3.Left);
drivingMotor.Settings.VelocityMotor.Softness = .3f;
drivingMotor.Settings.MaximumForce = 100;
//Let it roll when the user isn't giving specific commands.
drivingMotor.IsActive = false;
steeringMotor = new RevoluteMotor(body, wheel, Vector3.Up);
steeringMotor.Settings.Mode = MotorMode.Servomechanism;
//The constructor makes a guess about how to set up the constraint.
//It can't always be right since it doesn't have all the information;
//in this case, it chooses the basis and test axis incorrectly.
//This leads to a 'flipping' behavior when the wheel is rolling
//(the test axis is 'rolling' with the wheel, and passes over
//a singularity which causes a flip).
//To fix this, we configure the constraint directly.
//The basis is aligned with how the wheel is set up; we choose 'up' as
//the motorized axis, and right/forward to define the angle measurement plane.
//The test axis is set to be perpendicular to the wheel's rotation so that
//it only measures the steering angle.
//If you're curious, the angle measurement is just a Math.Atan2.
//The current world test axis is dotted against the two plane axes (Right and Forward here).
//This gives an x and y value. These can be plugged into Atan2 just like when
//you compute an angle on a normal 2d graph.
steeringMotor.Basis.SetWorldAxes(Vector3.Up, Vector3.Right);
steeringMotor.TestAxis = Vector3.Right;
steeringMotor.Settings.Servo.BaseCorrectiveSpeed = 5;
//The revolute motor is weaker than some other types of constraints and maintaining a goal in the presence of extremely fast rotation and integration issues.
//Laying a revolute limit on top of it can help mitigate the problem.
var steeringConstraint = new RevoluteLimit(body, wheel, Vector3.Up, Vector3.Right, -maximumTurnAngle, maximumTurnAngle);
//Add the wheel and connection to the space.
Space.Add(wheel);
Space.Add(pointOnLineJoint);
Space.Add(suspensionLimit);
Space.Add(suspensionSpring);
Space.Add(swivelHingeAngularJoint);
Space.Add(drivingMotor);
Space.Add(steeringMotor);
Space.Add(steeringConstraint);
return wheel;
}