A contemporary Japanese onsen bathhouse at twilight, massive weathered cedar walls opening to a private courtyard with moss-covered stones, copper soaking tubs steaming in cool evening air, floor-to-ceiling glass panels revealing zen garden with raked gravel patterns, soft paper lanterns casting warm amber glow across hinoki wood floors, minimalist bamboo accessories and plush white towels, hand-painted watercolor textures with visible brushstrokes and paper grain, soft sage green and warm ivory palette, Blender Cycles cinematic render with frame-by-frame oil painting aesthetics, volumetric twilight light creating elegant shadows across natural materials, global illumination generating ethereal spa sanctuary atmosphere, architectural digest quality composition, peaceful contemplative mood at dusk in transformed modern bathhouse