public override void ApplyForce()
{
x2 = new Vector3(PS.MousePosition);
if (!PS.MouseDown) p1 = null;
if (PS.MouseDown && p1 == null)
{
float min = Single.PositiveInfinity;
p1 = null;
foreach (Particle p in PS.Particles)
{
float dist = (p.Position - x2).LengthSquared;
if (dist < min)
{
p1 = p;
min = dist;
restLength = (x2 - p1.Position).LengthSquared;
}
}
restLength = (float)Math.Sqrt(restLength);
}
activated = p1 != null;
if (activated)
{
Vector3 diff = x2 - p1.Position;
float currentLength = diff.Length;
diff.Normalize();
float dvDot = -Vector3.Dot(diff, p1.Velocity);
diff *= Constants.Physics.STIFFNESS_STRETCH * (currentLength - restLength) + Constants.Physics.DAMPING_MASS * dvDot;
p1.Force += diff * p1.Mass;
}
}
/// <summary>
/// Constructs a new stretching spring force.
/// </summary>
/// <param name="p1">A particle.</param>
/// <param name="p2">A particle.</param>
public SpringForceStretch(Particle p1, Particle p2)
{
this.p1 = p1;
this.p2 = p2;
restLength = (p2.Position - p1.Position).Length;
}
public CircleConstraint(Particle p1, Vector3 x2)
{
this.p1 = p1;
this.x2 = x2;
radius = (x2 - p1.Position).Length;
}
/// <summary>
/// Constructs a new spring bending force.
/// </summary>
/// <param name="p0">A particle that should be part of a SpringForceStretch along with p1.</param>
/// <param name="p1">A particle that should be part of SpringForceStretch objects with both p0 and p2.</param>
/// <param name="p2">A particle that should be part of a SpringForceStretch along with p1.</param>
public SpringForceBend(Particle p0, Particle p1, Particle p2)
{
this.p0 = p0;
this.p1 = p1;
this.p2 = p2;
}
/// <summary>
/// Constructs a new pin constraint.
/// </summary>
/// <param name="p1">The particle to pin.</param>
public PinConstraint(Particle p1)
{
this.p1 = p1;
}
/// <summary>
/// Creates a particle given a position and adds it to the particle system.
/// </summary>
/// <param name="position">The position of the newly created particle.</param>
/// <returns>The newly created particle.</returns>
public Particle CreateParticle(Vector3 position)
{
Particle p = new Particle(position);
particles.Add(p);
return p;
}