import { Viewer as CesiumViewer, ImageryLayer } from 'cesium';
declare global {
    interface Window {
        /** Set to true once the deterministic scene has rendered a stable frame. */
        __VRT_READY__?: boolean;
        /** The Cesium viewer of the current VRT story, for debugging. */
        __VRT_VIEWER__?: CesiumViewer;
    }
}
/**
 * Cesium's bundled, network-free coarse imagery (Natural Earth II). Using it
 * keeps VRT renders deterministic and offline (no ion token, no tile server).
 */
export declare const offlineBaseLayer: () => ImageryLayer;
/**
 * Removes every known source of frame-to-frame and machine-to-machine variance
 * so that screenshots are byte-stable under software (SwiftShader) rendering.
 */
export declare const applyDeterminism: (viewer: CesiumViewer) => void;
/**
 * Resolves once the globe has finished loading tiles and a few stable frames
 * have been rendered, then flips `window.__VRT_READY__` for the test runner.
 * Returns a cleanup function.
 */
export declare const signalWhenStable: (viewer: CesiumViewer) => (() => void);