One planetary resolution terrain, two gigantic resolution ones and five massive resolution ones make up the dunes. The actual camera field of view is 120 degrees (FOV 150 at Scale 100) and the sun is at this position highly distorted. A sphere distorted the other way around hides the sun and thus the sun appears round as it should. The backdrop HDRI helps darkening the sky and provides the ambient light to brighten up the shadows. Rendered with soft sun shadows.