/**
 * Baked irradiance volume: a grid of second-order (9-coefficient, RGB) spherical-harmonic probes
 * over a box region, sampled at runtime for ambient lighting. It is the datum an interior has that
 * a hemisphere light cannot: a room's fill is its own, not the sky's, and it varies across the space.
 *
 * Serializable and pure; the bake is deterministic heuristics (sky visibility, authored lamps and
 * bounce colours), not a path tracer.
 */
/** SH coefficients per channel for the second band — 3 bands, real basis. */
export declare const SH_COEFFICIENTS = 9;
/** Floats stored per probe: {@link SH_COEFFICIENTS} × RGB. */
export declare const PROBE_STRIDE: number;
/** One irradiance volume authored on a scene document. */
export interface IrradianceVolume {
    id: string;
    /** World-space centre of the grid. */
    center: readonly [number, number, number];
    /** World-space extent of the grid. */
    size: readonly [number, number, number];
    /** Probe count per axis; at least 1. */
    resolution: readonly [number, number, number];
    /**
     * `PROBE_STRIDE` floats per probe, row-major (x fastest, then y, then z). Absent until baked, so a
     * freshly authored volume renders nothing rather than a fabricated ambient.
     */
    samples?: readonly number[];
}
/** Authored bake inputs stored beside the samples so a volume can be re-baked without the editor. */
export interface IrradianceBakeSettings {
    /** How much sky reaches the region: 0 fully enclosed, 1 fully open. */
    skyVisibility: number;
    /** Radiance above the horizon for an open region. Default the sky's own horizon colour. */
    skyColor?: string;
    /** Radiance below the horizon (ground bounce). */
    groundColor?: string;
    /** Fill colour of an enclosed region's ceiling; keeps a room from baking to black. */
    ceilingColor?: string;
    /** Fill colour of an enclosed region's floor. */
    floorColor?: string;
    /** Multiplier on the enclosed fill. Default 1. */
    fillIntensity?: number;
    /** Authored lamps folded into the bake. */
    lights?: readonly {
        position: readonly [number, number, number];
        color?: string;
        intensity?: number;
        distance?: number;
    }[];
}
/**
 * Real-basis SH values for a unit direction, into `out` (length 9):
 * `[Y00, Y1-1, Y10, Y11, Y2-2, Y2-1, Y20, Y21, Y22]`.
 * @internal
 */
export declare function shDirection(x: number, y: number, z: number, out: Float64Array | number[]): void;
/** World-space position of probe `(ix, iy, iz)`; the outer probes sit on the box faces.
 * @internal
 */
export declare function probePosition(volume: Pick<IrradianceVolume, "center" | "size" | "resolution">, ix: number, iy: number, iz: number): [number, number, number];
/** Everything a bake needs for one volume: where the grid sits, how much sky reaches it, and what fills the dark. */
export interface IrradianceBakeInput {
    /** Stable volume id, copied onto the baked volume. */
    id: string;
    center: readonly [number, number, number];
    size: readonly [number, number, number];
    resolution: readonly [number, number, number];
    settings: IrradianceBakeSettings;
    /** Direction samples per probe. Default 64. */
    samples?: number;
}
/**
 * Bakes an irradiance volume from authored inputs: sky radiance where the region is open, an
 * authored ceiling/floor fill where it is enclosed, plus inverse-square lamp radiance. Each probe
 * projects its directional radiance into L2 SH, so ambient varies across the grid and keeps a lit
 * side instead of flattening to one number.
 * @capability light-probes bake an irradiance volume from authored sky, fill and lamp inputs
 */
export declare function bakeIrradianceVolume(input: IrradianceBakeInput): IrradianceVolume;
/**
 * The volume that governs a world position: the one whose box contains it, else the nearest by
 * centre. A scene usually authors one volume per interior plus one for the exterior shell.
 * @internal
 */
export declare function selectIrradianceVolume(volumes: readonly IrradianceVolume[], position: readonly [number, number, number]): IrradianceVolume | undefined;
/**
 * Trilinearly samples the volume's SH at a world position, writing {@link PROBE_STRIDE} floats into
 * `out`. Positions outside the grid clamp to its faces, so a probe volume never pops to black at its
 * edge. Returns false when the volume has no baked samples.
 * @internal
 */
export declare function sampleIrradianceVolume(volume: IrradianceVolume, position: readonly [number, number, number], out: Float32Array): boolean;
/**
 * Radiance along a direction from the SH, `Σ coeff·basis` clamped at zero. Used by tests and by
 * tooling that previews a volume without a renderer.
 * @internal
 */
export declare function radianceAlong(sh: ArrayLike<number>, normal: readonly [number, number, number]): [number, number, number];