import type { IlluminanceInput, IlluminanceResult } from './types.js';
/**
 * Simple CU lookup by room index (linear interpolation).
 * Based on typical reflectance values (ceiling 70%, wall 50%, floor 20%).
 */
export declare const CU_TABLE: [number, number][];
/** Room-index range the CU table actually covers — outside it, lookupCU() clamps. */
export declare const CU_TABLE_RANGE: readonly [number, number];
/**
 * Calculate illuminance using the Lumen Method.
 *
 * N = (E × A) / (Φ × CU × MF)
 * Room Index = (L × W) / (Hm × (L + W))
 * Hm = luminaire height − workplane height
 *
 * @param input - Room dimensions and lighting parameters
 * @returns Number of fixtures needed and lighting metrics
 * @throws {RangeError} roomLength, roomWidth, lumensPerLuminaire, or targetLux ≤ 0,
 *   or the mounting height above the workplane (luminaireHeight − workplaneHeight) ≤ 0.
 */
export declare function illuminance(input: IlluminanceInput): IlluminanceResult;
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