import type { Bounds, Vec3 } from './types';
/**
 * Where a player should stand when they enter an imported Scene.
 *
 * Deriving the spawn from the bounding box alone cannot work: the box's minimum
 * Y is the lowest point anywhere on the sheet (a shoreline, a basement, the
 * underside of a bridge), and its centre in X/Z is a corner for any source
 * whose local origin sits at one edge. Both mistakes put the player in open air
 * with nothing under them, which is indistinguishable from a broken collision
 * mesh.
 *
 * So probe the real geometry instead: drop a ray straight down at a candidate
 * point, take the highest surface it hits, and require standing headroom above
 * it so the spawn is never inside a building or under a canopy.
 */
export type SpawnProbeResult = {
    position: Vec3;
    /** Surface height the ray actually hit, before clearance was added. */
    groundY: number;
    /** How many candidates were rejected before this one, for the receipt. */
    rejectedCandidates: number;
};
export type ProbeTriangle = readonly [Vec3, Vec3, Vec3];
/**
 * Highest surface at (x, z), or null when the downward ray misses the geometry
 * entirely — which is the signal that this candidate is over open air.
 */
export declare function columnAt(triangles: readonly ProbeTriangle[], x: number, z: number): {
    groundY: number;
    surfaces: number;
} | null;
/**
 * Barycentric height of a triangle at (x, z), or null when (x, z) falls outside
 * its vertical projection or the triangle is edge-on (zero projected area).
 */
export declare function triangleHeightAt(triangle: ProbeTriangle, x: number, z: number): number | null;
/**
 * Walks candidate points outward from the centre of the sheet in a square
 * spiral, returning the first that has real ground under it. Falls back to the
 * top of the bounds only when the geometry is missed everywhere, which is an
 * honest "I could not find ground" rather than a fabricated standing position.
 */
export declare function probeSpawn(input: {
    triangles: readonly ProbeTriangle[];
    bounds: Bounds;
    clearanceHeightM: number;
    /** Candidate grid resolution across the sheet. */
    samples?: number;
}): SpawnProbeResult;
/**
 * True when the ground within `radius` of (x, z) stays within
 * OPEN_GROUND_TOLERANCE_M of the candidate's own height in every direction. A
 * tree canopy, a rooftop edge and a wall all fail this; a street passes.
 */
export declare function isFlatNeighbourhood(triangles: readonly ProbeTriangle[], x: number, z: number, groundY: number, radius: number): boolean;