/**
 * cloth-verlet — pure Verlet+constraint cloth solver.
 *
 * Extracted from `packages/runtime/src/traits/PhysicsTraits.ts` ClothTrait
 * (was lines 120-214) to apply the RULING 2 per-trait wrapper pattern
 * established by NeuralAnimation: engine-agnostic core math, both core/traits
 * and runtime/traits get thin wrappers around the same engine.
 *
 * No THREE.js / PhysicsWorld dependency. Operates on raw Float32Array
 * position buffers — caller supplies them, engine modifies in place.
 *
 * /stub-audit 2026-04-26 flagged ClothTrait at 15 effective LOC + 17 compiler
 * refs as a CONFIRMED Pattern B violation. The core/traits/ClothTrait.ts
 * handler emits cloth_create/cloth_step/cloth_apply_force events that ZERO
 * runtime listeners ever consume. The actual cloth simulation lives in
 * runtime/traits/PhysicsTraits.ts (Pattern E manifestation: two unbridged
 * TraitSystems). This engine extraction is the first step toward bridging
 * — the math now lives in a place both can call.
 */
/**
 * Mutable simulation state. Caller owns the buffers; engine modifies in place
 * on every step. Float32Array layout is row-major xyz: positions[i*3..i*3+3].
 */
export interface ClothVerletState {
    /** Current vertex positions (count * 3 floats). Modified in place by stepClothVerlet. */
    positions: Float32Array;
    /** Previous-tick vertex positions (count * 3 floats). Modified in place. */
    prevPositions: Float32Array;
    /** Vertex indices that are pinned (immovable). */
    pinned: Set<number>;
    /** Distance constraints — each entry is [vertexA, vertexB, restLength]. */
    constraints: Array<[number, number, number]>;
    /** Wall-clock simulation time (seconds). Caller-managed; engine reads only. */
    time: number;
}
export interface ClothVerletConfig {
    /** 0–1 — how strongly constraints pull vertices back to rest length. */
    stiffness: number;
    /** 0–1 — velocity damping per step (0 = no damping, 1 = full stop). */
    damping: number;
    /** Gravity scale (1 = -9.81 m/s² on Y). */
    gravityScale: number;
    /** 0–1 — turbulent wind force magnitude. */
    windResponse: number;
}
/**
 * Build the structural-spring constraint set for a square cloth grid.
 *
 * Connects each vertex to its right + bottom neighbor (no diagonals — that's
 * the shear constraint set, intentionally omitted here for backward parity
 * with the previous runtime impl). Rest length is computed from the actual
 * positions in the buffer at construction time, so non-uniform initial
 * grids are supported.
 */
export declare function buildClothConstraints(resolution: number, positions: Float32Array): Array<[number, number, number]>;
/**
 * Advance one Verlet integration step + iterative constraint solve.
 *
 * Modifies state.positions and state.prevPositions in place.
 * Caller is responsible for advancing state.time before/after the call —
 * engine reads it for wind turbulence but does not modify.
 *
 * Iteration count for constraint solve = ceil(stiffness * 5).
 */
export declare function stepClothVerlet(state: ClothVerletState, config: ClothVerletConfig, delta: number): void;