import type { Vector3 } from '@holoscript/core';
/**
 * GlobalIllumination.ts
 *
 * Global Illumination system:
 *   - Spherical Harmonic (SH, L2 9-coefficient) light probe encoding/decoding
 *   - SH irradiance grid (3D probe array)
 *   - Irradiance probe sampling and trilinear interpolation
 *   - DDGI-style probe validity tracking
 *   - Lightmap UV unwrapping placeholder (atlas packing)
 *   - Bounce count / GI mode configuration
 *
 * CPU-side — does not depend on WebGPU. Probe lighting values are
 * expected to come from an offline bake or iterative runtime update.
 *
 * @module rendering
 */
/** L2 spherical harmonics — 9 coefficients per RGB channel */
export interface SH9 {
    r: Float32Array;
    g: Float32Array;
    b: Float32Array;
}
export type GIMode = 'lightmaps' | 'probes' | 'ddgi' | 'ssgi' | 'none';
export interface GIConfig {
    mode: GIMode;
    /** World-space distance between adjacent probes */
    probeSpacing: number;
    /** Number of indirect light bounces to simulate */
    bounceCount: number;
    /** Grid dimensions [x, y, z] */
    gridSize: [number, number, number];
    /** World-space origin of the probe grid */
    gridOrigin: Vector3;
}
/** Create an empty SH9 (all zeroes) */
export declare function createSH9(): SH9;
/**
 * Add a directional radiance sample to an SH9 accumulator.
 * dir must be a unit vector (azimuth encoded across hemisphere).
 */
export declare function addSHSample(sh: SH9, dir: Vector3, radiance: [number, number, number], weight?: number): void;
/**
 * Evaluate SH9 irradiance at a surface normal (Ravi Ramamoorthi, 2001).
 * Returns RGB irradiance.
 */
export declare function evalSH9Irradiance(sh: SH9, normal: Vector3): [number, number, number];
/** Scale all SH coefficients by a scalar (e.g. to normalise after sample accumulation) */
export declare function scaleSH9(sh: SH9, s: number): void;
/** Linearly interpolate between two SH9 probes (for trilinear grid lookup) */
export declare function lerpSH9(a: SH9, b: SH9, t: number): SH9;
export interface ProbeInfo {
    index: number;
    worldPos: Vector3;
    sh: SH9;
    /** 0 = invalid (occlusion issue), 1 = valid */
    validity: number;
    /** Number of times this probe has been updated */
    updateCount: number;
}
export declare class GIProbeGrid {
    private probes;
    private config;
    constructor(config?: Partial<GIConfig>);
    private buildGrid;
    getProbeCount(): number;
    getConfig(): Readonly<GIConfig>;
    getProbe(x: number, y: number, z: number): ProbeInfo | undefined;
    getProbeAt(index: number): ProbeInfo | undefined;
    updateProbe(x: number, y: number, z: number, sh: SH9): void;
    setValidity(x: number, y: number, z: number, valid: number): void;
    invalidateAll(): void;
    /** Number of valid probes (validity > 0) */
    getValidProbeCount(): number;
    /**
     * Sample irradiance at a world-space position + surface normal.
     * Performs trilinear interpolation across the 8 surrounding probes.
     */
    sampleIrradiance(worldPos: Vector3, normal: Vector3): [number, number, number];
    /**
     * Return lightmap UV (atlas page + offset) for a given probe index.
     * Probes are packed in a square atlas, 16 per row.
     */
    getLightmapUV(probeIndex: number): {
        page: number;
        u: number;
        v: number;
    };
}
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