/// <summary>
/// creates a faux angle constraint by figuring out the required distance from a to c for the given angle
/// </summary>
/// <param name="a">The alpha component.</param>
/// <param name="center">Center.</param>
/// <param name="c">C.</param>
/// <param name="stiffness">Stiffness.</param>
/// <param name="angleInDegrees">Angle in degrees.</param>
public static DistanceConstraint create( Particle a, Particle center, Particle c, float stiffness, float angleInDegrees )
{
var aToCenter = Vector2.Distance( a.position, center.position );
var cToCenter = Vector2.Distance( c.position, center.position );
var distance = Mathf.sqrt( aToCenter * aToCenter + cToCenter * cToCenter - ( 2 * aToCenter * cToCenter * Mathf.cos( angleInDegrees * Mathf.deg2Rad ) ) );
return new DistanceConstraint( a, c, stiffness, distance );
}
public LineSegments( Vector2[] vertices, float stiffness )
{
for( var i = 0; i < vertices.Length; i++ )
{
var p = new Particle( vertices[i] );
addParticle( p );
if( i > 0 )
addConstraint( new DistanceConstraint( particles.buffer[i], particles.buffer[i - 1], stiffness ) );
}
}
public DistanceConstraint( Particle first, Particle second, float stiffness, float distance = -1 )
{
_particleOne = first;
_particleTwo = second;
this.stiffness = stiffness;
if( distance > -1 )
restingDistance = distance;
else
restingDistance = Vector2.Distance( first.position, second.position );
}
public AngleConstraint( Particle a, Particle center, Particle c, float stiffness )
{
_particleA = a;
_centerParticle = center;
_particleC = c;
this.stiffness = stiffness;
// not need for this Constraint to collide. There will be DistanceConstraints to do that if necessary
collidesWithColliders = false;
angleInRadians = angleBetweenParticles();
}
Particle createTreeBranch( Particle parent, int i, int nMax, float segmentCoef, Vector2 normal, float branchLength, float theta )
{
var particle = new Particle( parent.position + ( normal * ( branchLength * segmentCoef ) ) );
addParticle( particle );
addConstraint( new DistanceConstraint( parent, particle, 0.7f ) );
if( i < nMax )
{
var aRot = Mathf.rotateAround( normal, Vector2.Zero, -theta * Mathf.rad2Deg );
var bRot = Mathf.rotateAround( normal, Vector2.Zero, theta * Mathf.rad2Deg );
var a = createTreeBranch( particle, i + 1, nMax, segmentCoef * segmentCoef, aRot, branchLength, theta );
var b = createTreeBranch( particle, i + 1, nMax, segmentCoef * segmentCoef, bRot, branchLength, theta );
var jointStrength = Mathf.lerp( 0.9f, 0, (float)i / nMax );
addConstraint( new AngleConstraint( parent, particle, a, jointStrength ) );
addConstraint( new AngleConstraint( parent, particle, b, jointStrength ) );
}
return particle;
}
