Dart Documentationbox2dTimeOfImpactSolver

TimeOfImpactSolver class

class TimeOfImpactSolver {
 List<TimeOfImpactConstraint> constraints;
 int count;
 Body toiBody;

 /** Pooling. */
 final TimeOfImpactSolverManifold psm;
 final Vector rA;
 final Vector rB;
 final Vector P;
 final Vector temp;

 TimeOfImpactSolver() :
   count = 0,
   toiBody = null,
   constraints = new List<TimeOfImpactConstraint>.generate(
       4, (i) => new TimeOfImpactConstraint()),

   // Initialize pool variables.
   psm = new TimeOfImpactSolverManifold(),
   rA = new Vector(),
   rB = new Vector(),
   P = new Vector(),
   temp = new Vector();

 void initialize(List<Contact> contacts, int argCount, Body argToiBody) {
   count = argCount;
   toiBody = argToiBody;

   if(count >= constraints.length){
     List<TimeOfImpactConstraint> old = constraints;
     int newLen = Math.max(count, old.length*2);
     constraints = new List<TimeOfImpactConstraint>(newLen);
     constraints.setRange(0, old.length, old);
     for(int i=old.length; i<constraints.length; i++){
       constraints[i] = new TimeOfImpactConstraint();
     }
   }

   for (int i=0; i<count; i++) {
     Contact contact = contacts[i];

     Fixture fixtureA = contact.fixtureA;
     Fixture fixtureB = contact.fixtureB;
     Shape shapeA = fixtureA.shape;
     Shape shapeB = fixtureB.shape;
     num radiusA = shapeA.radius;
     num radiusB = shapeB.radius;
     Body bodyA = fixtureA.body;
     Body bodyB = fixtureB.body;
     Manifold manifold = contact.manifold;

     assert(manifold.pointCount > 0);

     TimeOfImpactConstraint constraint = constraints[i];
     constraint.bodyA = bodyA;
     constraint.bodyB = bodyB;
     constraint.localNormal.setFrom(manifold.localNormal);
     constraint.localPoint.setFrom(manifold.localPoint);
     constraint.type = manifold.type;
     constraint.pointCount = manifold.pointCount;
     constraint.radius = radiusA + radiusB;

     for (int j = 0; j < constraint.pointCount; ++j){
       ManifoldPoint cp = manifold.points[j];
       constraint.localPoints[j] = cp.localPoint;
     }
   }
 }

 /**
  * Perform one solver iteration. Returns true if converged.
  */
 bool solve(num baumgarte){
   num minSeparation = 0;

   for (int i = 0; i < count; ++i){
     TimeOfImpactConstraint c = constraints[i];
     Body bodyA = c.bodyA;
     Body bodyB = c.bodyB;

     num massA = bodyA.mass;
     num massB = bodyB.mass;

     // Only the TimeOfImpact body should move.
     if (bodyA == toiBody){
       massB = 0.0;
     } else{
       massA = 0.0;
     }

     num invMassA = massA * bodyA.invMass;
     num invIA = massA * bodyA.invInertia;
     num invMassB = massB * bodyB.invMass;
     num invIB = massB * bodyB.invInertia;

     // Solve normal constraints
     for (int j = 0; j < c.pointCount; ++j){
       psm.initialize(c, j);
       Vector normal = psm.normal;

       Vector point = psm.point;
       num separation = psm.separation;

       rA.setFrom(point).subLocal(bodyA.sweep.center);
       rB.setFrom(point).subLocal(bodyB.sweep.center);

       // Track max constraint error.
       minSeparation = Math.min(minSeparation, separation);

       // Prevent large corrections and allow slop.
       num C = MathBox.clamp(baumgarte * (separation +
           Settings.LINEAR_SLOP), -Settings.MAX_LINEAR_CORRECTION, 0.0);

       // Compute the effective mass.
       num rnA = Vector.crossVectors(rA, normal);
       num rnB = Vector.crossVectors(rB, normal);
       num K = invMassA + invMassB + invIA * rnA * rnA + invIB * rnB * rnB;

       // Compute normal impulse
       num impulse = K > 0.0 ? - C / K : 0.0;

       P.setFrom(normal).mulLocal(impulse);

       temp.setFrom(P).mulLocal(invMassA);
       bodyA.sweep.center.subLocal(temp);
       bodyA.sweep.angle -= invIA * Vector.crossVectors(rA, P);
       bodyA.synchronizeTransform();

       temp.setFrom(P).mulLocal(invMassB);
       bodyB.sweep.center.addLocal(temp);
       bodyB.sweep.angle += invIB * Vector.crossVectors(rB, P);
       bodyB.synchronizeTransform();
     }
   }

   // We can't expect minSpeparation >= -_LINEAR_SLOP because we don't
   // push the separation above -_LINEAR_SLOP.
   return minSeparation >= -1.5 * Settings.LINEAR_SLOP;
 }
}

Constructors

new TimeOfImpactSolver() #

TimeOfImpactSolver() :
 count = 0,
 toiBody = null,
 constraints = new List<TimeOfImpactConstraint>.generate(
     4, (i) => new TimeOfImpactConstraint()),

 // Initialize pool variables.
 psm = new TimeOfImpactSolverManifold(),
 rA = new Vector(),
 rB = new Vector(),
 P = new Vector(),
 temp = new Vector();

Properties

List<TimeOfImpactConstraint> constraints #

List<TimeOfImpactConstraint> constraints

int count #

int count

final Vector P #

final Vector P

final TimeOfImpactSolverManifold psm #

Pooling.

final TimeOfImpactSolverManifold psm

final Vector rA #

final Vector rA

final Vector rB #

final Vector rB

final Vector temp #

final Vector temp

Body toiBody #

Body toiBody

Methods

void initialize(List<Contact> contacts, int argCount, Body argToiBody) #

void initialize(List<Contact> contacts, int argCount, Body argToiBody) {
 count = argCount;
 toiBody = argToiBody;

 if(count >= constraints.length){
   List<TimeOfImpactConstraint> old = constraints;
   int newLen = Math.max(count, old.length*2);
   constraints = new List<TimeOfImpactConstraint>(newLen);
   constraints.setRange(0, old.length, old);
   for(int i=old.length; i<constraints.length; i++){
     constraints[i] = new TimeOfImpactConstraint();
   }
 }

 for (int i=0; i<count; i++) {
   Contact contact = contacts[i];

   Fixture fixtureA = contact.fixtureA;
   Fixture fixtureB = contact.fixtureB;
   Shape shapeA = fixtureA.shape;
   Shape shapeB = fixtureB.shape;
   num radiusA = shapeA.radius;
   num radiusB = shapeB.radius;
   Body bodyA = fixtureA.body;
   Body bodyB = fixtureB.body;
   Manifold manifold = contact.manifold;

   assert(manifold.pointCount > 0);

   TimeOfImpactConstraint constraint = constraints[i];
   constraint.bodyA = bodyA;
   constraint.bodyB = bodyB;
   constraint.localNormal.setFrom(manifold.localNormal);
   constraint.localPoint.setFrom(manifold.localPoint);
   constraint.type = manifold.type;
   constraint.pointCount = manifold.pointCount;
   constraint.radius = radiusA + radiusB;

   for (int j = 0; j < constraint.pointCount; ++j){
     ManifoldPoint cp = manifold.points[j];
     constraint.localPoints[j] = cp.localPoint;
   }
 }
}

bool solve(num baumgarte) #

Perform one solver iteration. Returns true if converged.

bool solve(num baumgarte){
 num minSeparation = 0;

 for (int i = 0; i < count; ++i){
   TimeOfImpactConstraint c = constraints[i];
   Body bodyA = c.bodyA;
   Body bodyB = c.bodyB;

   num massA = bodyA.mass;
   num massB = bodyB.mass;

   // Only the TimeOfImpact body should move.
   if (bodyA == toiBody){
     massB = 0.0;
   } else{
     massA = 0.0;
   }

   num invMassA = massA * bodyA.invMass;
   num invIA = massA * bodyA.invInertia;
   num invMassB = massB * bodyB.invMass;
   num invIB = massB * bodyB.invInertia;

   // Solve normal constraints
   for (int j = 0; j < c.pointCount; ++j){
     psm.initialize(c, j);
     Vector normal = psm.normal;

     Vector point = psm.point;
     num separation = psm.separation;

     rA.setFrom(point).subLocal(bodyA.sweep.center);
     rB.setFrom(point).subLocal(bodyB.sweep.center);

     // Track max constraint error.
     minSeparation = Math.min(minSeparation, separation);

     // Prevent large corrections and allow slop.
     num C = MathBox.clamp(baumgarte * (separation +
         Settings.LINEAR_SLOP), -Settings.MAX_LINEAR_CORRECTION, 0.0);

     // Compute the effective mass.
     num rnA = Vector.crossVectors(rA, normal);
     num rnB = Vector.crossVectors(rB, normal);
     num K = invMassA + invMassB + invIA * rnA * rnA + invIB * rnB * rnB;

     // Compute normal impulse
     num impulse = K > 0.0 ? - C / K : 0.0;

     P.setFrom(normal).mulLocal(impulse);

     temp.setFrom(P).mulLocal(invMassA);
     bodyA.sweep.center.subLocal(temp);
     bodyA.sweep.angle -= invIA * Vector.crossVectors(rA, P);
     bodyA.synchronizeTransform();

     temp.setFrom(P).mulLocal(invMassB);
     bodyB.sweep.center.addLocal(temp);
     bodyB.sweep.angle += invIB * Vector.crossVectors(rB, P);
     bodyB.synchronizeTransform();
   }
 }

 // We can't expect minSpeparation >= -_LINEAR_SLOP because we don't
 // push the separation above -_LINEAR_SLOP.
 return minSeparation >= -1.5 * Settings.LINEAR_SLOP;
}