import type { AnimationAction } from "three";
import { AnimationTree } from "./AnimationTree";
/**
 * Configuration for a linear animation action in the blend tree.
 * Associates an animation action with a position value on the linear blend axis.
 */
export interface LinearAction {
    /** The animation action to be played */
    action: AnimationAction;
    /** Position value on the linear blend axis where this action is positioned */
    value: number;
}
/**
 * Linear blend tree implementation for 1D animation blending.
 *
 * Manages a collection of animation actions positioned along a linear axis,
 * automatically blending between adjacent animations based on a blend value.
 * The blend tree interpolates weights between the two closest animations
 * to create smooth transitions across the linear space.
 *
 * Note: Action values are not limited to the 0-1 range. You can use any
 * numeric values, including negative values, that make sense for your
 * application (e.g., speed in m/s, or any custom metric). However, all
 * values must be finite numbers within JavaScript's safe range and must
 * be unique (no duplicate values allowed).
 *
 * @example
 * ```typescript
 * const idleAction = mixer.clipAction(idleClip);
 * const walkAction = mixer.clipAction(walkClip);
 * const runAction = mixer.clipAction(runClip);
 *
 * const blendTree = new LinearBlendTree([
 *   { action: idleAction, value: 0 },
 *   { action: walkAction, value: 0.5 },
 *   { action: runAction, value: 1 }
 * ]);
 *
 * // Set blend to 0.3 - results in:
 * // idleAction weight: 0.4 (40%)
 * // walkAction weight: 0.6 (60%)
 * // runAction weight: 0.0 (0%)
 * blendTree.setBlend(0.3);
 * ```
 */
export declare class LinearBlendTree extends AnimationTree {
    private readonly anchors;
    private lastLeftAnchor?;
    private lastRightAnchor?;
    private currentBlend;
    /**
     * Creates a new linear blend tree with the specified animation actions.
     * Actions are automatically sorted by their value along the linear axis.
     * Initializes all actions to stopped state and validates clip durations.
     *
     * @param linearActions - Array of linear actions defining the blend space.
     *                       Must contain at least 2 actions with unique, finite values.
     * @throws {Error} When fewer than 2 actions are provided
     * @throws {Error} When any action has a non-finite value (NaN, ±Infinity)
     * @throws {Error} When any action has a value outside JavaScript's safe integer range
     * @throws {Error} When multiple actions have the same value (duplicate values)
     * @throws {Error} When any animation clip duration is not a positive finite number
     * @see {@link assertValidNumber} for value validation details
     * @see {@link assertValidPositiveNumber} for duration validation details
     */
    constructor(linearActions: LinearAction[]);
    get blendValue(): number;
    /**
     * Sets the blend value to determine animation weights along the linear axis.
     * When the blend changes, animation weights are recalculated to interpolate
     * between the two closest actions. Values outside the action range are
     * handled by giving full weight to the nearest boundary action.
     *
     * @param value - The target blend value (finite number)
     * @throws {Error} When the blend value is not a finite number
     * @see {@link assertValidNumber} for value validation details
     */
    setBlend(value: number): void;
    protected ["onEnterInternal"](): void;
    /**
     * Updates the influence for all anchors in the linear blend tree.
     * Called when the tree's influence changes but relative weights remain the same.
     * Applies the current tree influence to all anchors while maintaining
     * their existing weight distribution from the linear blending.
     */
    protected updateAnchorsInfluence(): void;
    /**
     * Recalculates and updates animation weights based on the current blend value.
     * Performs linear interpolation between the two actions closest to the blend point.
     * Actions outside the interpolation range receive zero weight.
     *
     * The interpolation uses the formula:
     * - Left weight = 1 - difference
     * - Right weight = difference
     * Where difference = (blend - leftValue) / (rightValue - leftValue)
     */
    private updateAnchors;
}