/** One foot's animated ankle height and the ground found under it, both in world units. */
export interface FootGroundSample {
    /** Animated ankle (foot bone) height this frame, before any correction. */
    ankleY: number;
    /** Ground height under the foot, or `null` when the probe found nothing. */
    groundY: number | null;
}
/** Inputs for {@link placeFeet}. All heights are world units. */
export interface FootPlacementInput {
    feet: readonly FootGroundSample[];
    /** Height of the model origin, which the clips were authored to stand on. */
    originY: number;
    /** Ankle height above the sole in the rig's rest pose; the sole never ends below the ground. */
    ankleHeight: number;
    /** Largest correction applied to a foot or the pelvis, up or down. */
    maxAdjust: number;
    /** A lowest sole this far above its ground reads as airborne. */
    airborneGap: number;
}
/** Result of {@link placeFeet}: where each ankle should go and how far the pelvis drops. */
export interface FootPlacement {
    /** Vertical pelvis shift, `<= 0`, so the lowest planted foot can reach its ground. */
    pelvisOffset: number;
    /** Target ankle height per foot, or `null` when that foot has no ground or no correction. */
    ankleTargets: (number | null)[];
    /** `false` while the feet are clear of the ground, so callers fade the correction out. */
    grounded: boolean;
}
/**
 * Resolves foot placement for a rig whose clips were authored on flat ground at its origin.
 * Each foot keeps its animated lift and moves by its ground's height above or below the origin,
 * the sole is never left under the ground, and the pelvis drops by the deepest reach so both legs
 * stay within length. Pure and allocation-light; the renderer applies the targets with
 * {@link solveTwoBone}.
 *
 * @capability animation ground rigged feet on slopes and steps without hiding the swing leg
 */
export declare function placeFeet(input: FootPlacementInput, out?: FootPlacement): FootPlacement;
/** A bone as {@link inferLegChains} sees it: its name and its parent's name. */
export interface RigBone {
    name: string;
    parent: string | null;
}
/** Thigh → shin → foot bone names for one leg. */
export interface LegChain {
    root: string;
    mid: string;
    tip: string;
}
/**
 * Finds leg chains on a humanoid rig by bone name: a thigh-like bone (`UpLeg`, `UpperLeg`, `Thigh`)
 * with its first child and grandchild as shin and foot. Control, IK-target and twist bones are
 * skipped. Returns chains in rig order; an empty array means the rig has no recognizable legs.
 *
 * @capability animation find thigh, shin and foot bones on a humanoid rig for foot IK
 */
export declare function inferLegChains(bones: readonly RigBone[]): LegChain[];