import type { Object3D } from "three";
import { Vector3 } from "three";
/**
 * Distributes aim rotation across a chain of bones.
 *
 * Computes the swing rotation from `currentDirection` to `targetDirection`
 * and splits it across bones according to `curve` weights.
 *
 * Mutates `bone.quaternion` directly. Call after AnimationMixer update.
 */
export declare class AimChainIK {
    readonly bones: readonly Object3D[];
    /** Numerical stability threshold. */
    epsilon: number;
    /**
     * Global blend weight. 0 = solver has no effect, 1 = full effect.
     * Clamped to 0-1 internally.
     */
    weight: number;
    /**
     * Per-bone rotation weights. Normalized internally so their sum equals 1.
     *
     * `[1, 1, 1, 1]` = uniform. `[0.2, 0.5, 0.8, 1.0]` = root gets least, tip gets most.
     *
     * Compared by reference - mutating values in-place won't trigger
     * renormalization. Assign a new array to update.
     *
     * Length must match bone count; mismatches throw on `solve()`.
     */
    curve: readonly number[];
    private readonly swingAxis;
    private readonly deltaRotation;
    private readonly boneWorldQuaternion;
    private readonly parentWorldQuaternion;
    private normalizedCurve;
    private lastCurveReference;
    /**
     * @param bones - Ordered from root to tip. Must contain at least one bone.
     */
    constructor(bones: readonly Object3D[]);
    /**
     * Rotate the chain so that `currentDirection` aligns with `targetDirection`.
     *
     * Both vectors are in world space and are not mutated.
     *
     * Sample directions **before** calling - this method mutates bone quaternions,
     * so any direction derived from the chain will be stale after the call.
     *
     * @param currentDirection - Where the chain currently aims.
     * @param targetDirection - Where it should aim.
     */
    solve(currentDirection: Vector3, targetDirection: Vector3): void;
    /**
     * Returns normalized curve (sums to 1).
     * Rebuilds only when the `curve` reference changes.
     */
    private getNormalizedCurve;
}