/**
 * Simple approximations and curves for daylight simulation.
 */
/**
 * CIE daylight locus approximation.
 * @param x Progress through the day (0 to 1)
 */
export declare function cieDaylightCurve(x: number): number;
/**
 * Simple sun altitude-based approximation.
 * @param x Progress through the day (0 to 1)
 */
export declare function sunAltitudeCurve(x: number): number;
/**
 * Perez daylight model approximation.
 * @param x Progress through the day (0 to 1)
 */
export declare function perezDaylightCurve(x: number): number;
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