import type { Vector3 } from '@holoscript/core';
/**
 * AdvancedPBR.ts
 *
 * Advanced Physically-Based Rendering material model.
 *
 * Extends basic PBR (albedo + normal + roughness) with:
 *   - Clearcoat layer (car paint, lacquer, wet surfaces)
 *   - Anisotropy (brushed metal, hair, fabric warp)
 *   - Sheen (velvet, cloth, microfibre)
 *   - Iridescence (soap bubbles, oil slicks, beetle shells)
 *   - Multi-layer material stack
 *   - Metallic/roughness workflow helpers
 *
 * All calculations are CPU-side (can feed GPU uniforms or be used in
 * offline renderers). No WebGPU imports — fully testable in Vitest.
 *
 * @module rendering
 */
export type RGB = [number, number, number];
export interface ClearcoatConfig {
    /** 0–1, overall clearcoat presence */
    intensity: number;
    /** 0–1, surface roughness of the clearcoat layer */
    roughness: number;
    /** Index of refraction (default 1.5 for glass-like coat) */
    ior: number;
}
export interface AnisotropyConfig {
    /** 0–1, anisotropy magnitude */
    strength: number;
    /** Rotation angle of anisotropic tangent in radians */
    angle: number;
    /** Anisotropy direction vector (must be unit) */
    tangent: Vector3;
}
export interface SheenConfig {
    /** RGB tint for sheen reflection */
    color: RGB;
    /** 0–1, surface roughness of sheen layer (velvet = low) */
    roughness: number;
}
export interface IridescenceConfig {
    /** 0–1, how visible the iridescent effect is */
    intensity: number;
    /** Index of refraction of thin film */
    ior: number;
    /** Thin-film thickness in nanometres (400–1200 typical) */
    thicknessNm: number;
}
export interface AdvancedPBRConfig {
    /** Base albedo (linear RGB) */
    albedo: RGB;
    /** 0–1, 0 = dielectric, 1 = metal */
    metallic: number;
    /** 0–1, microsurface roughness */
    roughness: number;
    /** Ambient occlusion 0–1 */
    ao: number;
    /** Emissive colour (HDR, can exceed 1) */
    emissive: RGB;
    clearcoat?: ClearcoatConfig;
    anisotropy?: AnisotropyConfig;
    sheen?: SheenConfig;
    iridescence?: IridescenceConfig;
}
/** GGX / Trowbridge-Reitz normal distribution function */
export declare function distributionGGX(NdotH: number, roughness: number): number;
/** Smith's geometry attenuation (Schlick-GGX) */
export declare function geometrySmith(NdotV: number, NdotL: number, roughness: number): number;
/** Schlick Fresnel approximation */
export declare function fresnelSchlick(cosTheta: number, F0: RGB): RGB;
/** Schlick Fresnel with roughness (for IBL) */
export declare function fresnelRoughness(cosTheta: number, F0: RGB, roughness: number): RGB;
/**
 * Evaluate clearcoat layer BRDF contribution.
 * Uses a separate GGX lobe with IOR-derived F0 ≈ ((ior-1)/(ior+1))².
 */
export declare function evaluateClearcoat(NdotH: number, NdotV: number, NdotL: number, VdotH: number, config: ClearcoatConfig): number;
/**
 * GGX NDF modified for anisotropic surfaces (Burley 2012).
 * alphaT and alphaB are per-axis roughness values.
 */
export declare function distributionGGXAnisotropic(NdotH: number, TdotH: number, BdotH: number, alphaT: number, alphaB: number): number;
/**
 * Compute per-axis roughness values from isotropic roughness + anisotropy strength.
 * Returns [alphaT, alphaB].
 */
export declare function anisotropicRoughness(roughness: number, strength: number): [number, number];
/**
 * Charlie sheen NDF (Estevez & Kulla 2017).
 * Produces the characteristic soft highlight at grazing angles.
 */
export declare function sheenDistribution(NdotH: number, roughness: number): number;
/** Sheen visibility function (L(NdotV) * L(NdotL)) */
export declare function sheenVisibility(NdotV: number, NdotL: number): number;
/** Evaluate full sheen BRDF contribution */
export declare function evaluateSheen(NdotH: number, NdotV: number, NdotL: number, config: SheenConfig): RGB;
/**
 * Thin-film interference iridescence (McGuire & Skelton 2020).
 * Computes a wavelength-dependent phase shift and maps it to RGB.
 * wavelengths: [680, 550, 440] nm (R, G, B).
 */
export declare function evaluateIridescence(cosTheta: number, config: IridescenceConfig): RGB;
/**
 * Compute F0 (reflectance at normal incidence) from albedo + metallic.
 * Dielectrics: F0 ≈ 0.04 (non-metals), metals: F0 = albedo.
 */
export declare function computeF0(albedo: RGB, metallic: number): RGB;
/**
 * Compute diffuse albedo for metallic surfaces (metals have no diffuse).
 */
export declare function computeDiffuseAlbedo(albedo: RGB, metallic: number): RGB;
export declare class AdvancedPBRMaterial {
    private config;
    constructor(config?: Partial<AdvancedPBRConfig>);
    setAlbedo(r: number, g: number, b: number): void;
    setMetallic(v: number): void;
    setRoughness(v: number): void;
    setAO(v: number): void;
    setEmissive(r: number, g: number, b: number): void;
    setClearcoat(cc: ClearcoatConfig): void;
    setAnisotropy(an: AnisotropyConfig): void;
    setSheen(sh: SheenConfig): void;
    setIridescence(ir: IridescenceConfig): void;
    getConfig(): Readonly<AdvancedPBRConfig>;
    getF0(): RGB;
    getDiffuse(): RGB;
    hasClearcoat(): boolean;
    hasAnisotropy(): boolean;
    hasSheen(): boolean;
    hasIridescence(): boolean;
    /**
     * Evaluate the full advanced PBR BRDF at a shading point.
     *
     * @param NdotL - dot(N, L), clamped [0,1]
     * @param NdotV - dot(N, V), clamped [0,1]
     * @param NdotH - dot(N, H), clamped [0,1]
     * @param VdotH - dot(V, H), clamped [0,1]
     * @param TdotH - dot(T, H) for anisotropy (0 if not anisotropic)
     * @param BdotH - dot(B, H) for anisotropy (0 if not anisotropic)
     * @returns RGB radiance contribution (direct light, no PI factor)
     */
    evaluate(NdotL: number, NdotV: number, NdotH: number, VdotH: number, TdotH?: number, BdotH?: number): RGB;
}
/** Pre-configured material presets */
export declare const MATERIAL_PRESETS: {
    carPaintRed: () => AdvancedPBRMaterial;
    brushedAluminium: () => AdvancedPBRMaterial;
    velvet: () => AdvancedPBRMaterial;
    soapBubble: () => AdvancedPBRMaterial;
};
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