public void Add(Spring spring)
{
if (!pointmass_list.Contains(spring.pointmass_a))
spring_pointmass_list.Add(spring.pointmass_a);
if (!pointmass_list.Contains(spring.pointmass_b))
spring_pointmass_list.Add(spring.pointmass_b);
spring_list.Add(spring);
}
public override void ApplyInternalForces(double elapsed)
{
// internal spring forces.
Vector2 force = new Vector2();
for (int i = 0; i < spring_list.Count; i++)
{
Spring s = spring_list[i];
Spring.SpringForce(ref s, out force);
s.pointmass_a.force.X += force.X;
s.pointmass_a.force.Y += force.Y;
s.pointmass_b.force.X -= force.X;
s.pointmass_b.force.Y -= force.Y;
}
// shape matching forces.
if (is_constrained)
{
for (int i = 0; i < count; i++)
{
if (shape_k > 0)
{
Spring.SpringForce(ref pointmass_list[i].position, ref pointmass_list[i].velocity, ref curr_shape.points[i],
ref pointmass_list[i].velocity, 0.0f, shape_k, shape_damping, out force);
pointmass_list[i].force.X += force.X;
pointmass_list[i].force.Y += force.Y;
}
}
}
for (int i = 0; i < spring_pointmass_list.Count; i++)
{
this.spring_pointmass_list[i].velocity.X *= damping;
this.spring_pointmass_list[i].velocity.Y *= damping;
this.spring_pointmass_list[i].Update(elapsed);
}
}
public void Update(double elapsed)
{
Vector2 force = new Vector2();
for (int i = 0; i < spring_list.Count; i++)
{
Spring s = spring_list[i];
Spring.SpringForce(ref s, out force);
s.pointmass_a.force.X += force.X;
s.pointmass_a.force.Y += force.Y;
s.pointmass_b.force.X -= force.X;
s.pointmass_b.force.Y -= force.Y;
}
for (int i = 1; i < pointmass_list.Count - 1; i++)
{
pointmass_list[i].velocity.X *= damping;
pointmass_list[i].velocity.Y *= damping;
pointmass_list[i].Update(elapsed);
}
}
public static void SpringForce(ref Spring spring, out Vector2 forceOut)
{
SpringForce(ref spring.pointmass_a.position, ref spring.pointmass_a.velocity, ref spring.pointmass_b.position, ref spring.pointmass_b.velocity, spring.d, spring.k, spring.damping, out forceOut);
}
public static void SpringForce(ref Spring spring, out Vector2 forceOut)
{
SpringForce(ref spring.pointmass_a.position, ref spring.pointmass_a.velocity, ref spring.pointmass_b.position, ref spring.pointmass_b.velocity, spring.d, spring.k, spring.damping, out forceOut);
}
