/**
 * The pit's walls: the ground's hole cut open. The hole's edge is a threshold (the signed distance
 * to the footprints against a radius that wanders with noise); this walks that same threshold on
 * a fine grid (marching squares) and stands a wall of unit height (in `PIT_WALL_ROWS` rows) on every piece of the contour,
 * facing into the hole. The wall's lower edge is not stored: each vertex carries a `drop` (0 at
 * the ground, 1 at the bottom) the shader scales by the pit's current depth, so a floor switch
 * moves a uniform and never rebuilds the walls.
 */
export type PitContourSource = {
    /** The grid box to walk: world XZ of its corner and its side. */
    originX: number;
    originZ: number;
    span: number;
    /** Signed distance to the footprints, as the ground's mask reads it. */
    distanceAt: (x: number, z: number) => number;
    /** The wandering radius of the hole's edge at full opening. */
    radiusAt: (x: number, z: number) => number;
    /** Where the wall's top sits: the ground surface there. */
    topAt: (x: number, z: number) => number;
    /** The radius's smallest and largest value anywhere: far from both, the contour cannot be. */
    radiusMin: number;
    radiusMax: number;
    /** Grid cell in metres (default 0.12). */
    cell?: number;
};
export type PitWalls = {
    positions: Float32Array;
    normals: Float32Array;
    /** x: 0 at the top of the wall, 1 at its foot. */
    drops: Float32Array;
    indices: Uint32Array;
};
/**
 * Rows a wall is cut into down its drop, so the shader can push them sideways by depth: a wall of
 * one row would stay a straight vertical fold from grade to the floor.
 */
export declare const PIT_WALL_ROWS = 16;
export declare function buildPitWalls(source: PitContourSource): PitWalls | null;
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