RopeChain#

PlushEngine · Type index

Namespace: PlushEngine.Physics (using PlushEngine.Physics;)

A hanging rope or cable as a chain of particles (position-based Verlet): both ends pinned, a fixed total length, gravity, collision through the caller's RopeContact, and friction where it rests on something. Where RopeLine is a taut line that wraps corners (a grapple), this one sags and drapes (wires over pipes, a cable off a trolley). Each end can also leave along a direction (out of a wall socket), which pins the next particle one link along it. Deterministic for the same inputs; no allocation per step. Grab holds one particle where the caller drags it; letting go keeps the motion it had, so a rope can be thrown.

public sealed class RopeChain

Members: Damping · Friction · Grab · Gravity · Iterations · Length · Link · Motion · Nearest · Points · Radius · Release · RopeChain · Smooth · Step

Damping#

public float Damping { get; set; }

Initial value: .01f

Fraction of velocity lost per step in air (0 none).

Friction#

public float Friction { get; set; }

Initial value: .6f

Fraction of sliding velocity lost per step while touching (0 ice, 1 sticks).

Grab#

public void Grab(int index, Vector3 target);

Holds particle index at target until Release; pinned ends cannot be grabbed.

Gravity#

public Vector3 Gravity { get; set; }

Initial value: new(0, -9.81f, 0)

Iterations#

public int Iterations { get; set; }

Initial value: 40

Length#

public float Length { get; }

Link#

public float Link { get; }

Rest length of one link.

Motion#

public float Motion { get; }

Largest distance any particle moved in the last Step, to tell when the rope has come to rest.

Nearest#

public int Nearest(Vector3 origin, Vector3 direction, float reach);

The free particle nearest a ray (for picking a rope to drag), or -1 when none is within reach.

Points#

public IReadOnlyList<Vector3> Points { get; }

Radius#

public float Radius { get; }

Release#

public void Release();

RopeChain#

public RopeChain(Vector3 start, Vector3 end, float length, int links, float radius = .01f, Vector3? startDirection = null, Vector3? endDirection = null);

A rope of length from start to end in links links, starting straight (so it never starts inside what it will hang over) and falling into its sag. A direction pins the particle after (before) the end one link along it.

Smooth#

public void Smooth(List<Vector3> output, int subdivisions = 3);

The rope's path with each link split by a Catmull-Rom curve into subdivisions pieces, for drawing.

Step#

public void Step(float dt, RopeContact? contact = null);

Advances the rope by dt seconds (keep it at or below 1/60).

Source#

• RopeChain.cs