Rope

The Rope node does not simulate anything itself — it describes cables. Every frame it emits a Configs structure that the parent Rope System consumes and feeds to the shared GPU XPBD solver. That is why a Rope node only works inside a Rope System container.

Anchors. The start is always pinned: either at the single Start X/Y/Z position or, when a cable is connected to Start Points, at every point of the array — one cable per point, up to 256 cables per Rope node (the system caps at 1024 total). The end behaves the same way through Attach End, End X/Y/Z and End Points, with one twist: the End array cycles by index. Equal counts pair i→i; a single End point makes every cable converge on it — an instant maypole.

Cable identity is slot-stable. Each cable's identity is its point index, so when a point array grows or shrinks, surviving cables keep their physics state — nothing restarts or pops.

Length. With Auto Length on, the rest length is the pin distance × Slack — cables automatically fit whatever they span, with a controllable droop. With it off, Length is the explicit rest length in Grafit units. Length Variability adds a seeded per-cable variation (0.5 on a 1.0 cable spreads lengths across 0.5…1.5) — deterministic, so the same Seed produces the same bundle forever. Length changes are live and never reset the simulation.

Material. Stretch is XPBD compliance: 0 is a steel cable, 1 a rubber band. Bend Stiffness resists folding. Damping is honest internal material damping — it calms swing without freezing uniform motion. Gravity Scale multiplies this cable's response to all force nodes in the system (0 = weightless).

Tearing. With Tear Enable on, a cable whose two pins separate beyond Tear Distance snaps its end free. The torn state is sticky — a torn cable stays torn — and is re-armed only by toggling Attach End off and on again. Every tear fires the parent system's one-frame Torn pulse.

Appearance. Thickness blends linearly from Start Thickness to End Thickness along each cable; Thickness Variability adds an independent seeded per-cable variation. Color sets a flat color; connecting a Gradient (up to 16 stops, e.g. from the Gradient node) colors along the rope. Rendering is Catmull-Rom smoothed instanced capsules.

Output: Configs (structure) — consumed by the parent Rope System; you never wire it manually.

• A hanging banner edge — one Rope with default anchors: a single cable drooping between two pins; animate Start X with an LFO for a gentle sway.
• Cable-per-fingertip — Vision hand tips → Landmarks to Points → system boundary → Start Points: ten cables ride the hands; leave Attach End off so they trail freely.
• Maypole ribbons — Geometry to Points (circle) → Start Points, single End X/Y at the center top, Slack 1.3: all ribbons converge; rotate the circle for winding.
• Organic bundle — one Rope, a short row of Start points, Length Variability 0.4 + Thickness Variability 0.5 + a warm Gradient: a bundle of unequal, individually-weighted strands from a single node.
• Breakable web — Tear Enable on, Tear Distance just above the pin distance, ends matched by Find Nearest Endpoint: cables that grab points and audibly snap when pulled — wire the system's Torn pulse to a sound or flash.

• Start Points / End Points / Gradient respond only to a really connected cable — a value merely sitting in the port default is ignored, so disconnecting cleanly reverts to the single-anchor ports.
• Determinism is per-cable: each cable's seed is derived from Seed plus its index, and length/thickness variability use independent streams — changing one never reshuffles the other.
• Torn is sticky by design: after a tear, pulling the pins back together does nothing. Toggle Attach End off → on (by hand or with a Bool cable) to re-arm the cable.
• Keep Segments proportional to length: 24 is right for a screen-crossing cable; short ropes look identical with 12 and cost half.
• Stretch above ~0.5 combined with Tear Enable makes tears feel rubbery and late — for crisp snaps keep Stretch low and let Tear Distance do the work.
• Very small Slack (near 1.0) makes taut cables — that is exactly the regime the solver's long-range attachment constraints are built for, so don't fear it: taut cables stay calm.