iirc mostly the osm building height data (see e.g. https://demo.f4map.com https://demo.f4map.com or https://streets.gl/ https://streets.gl/), the facade texture

iirc mostly the osm building height data (see e.g. https://demo.f4map.com https://demo.f4map.com or https://streets.gl/ https://streets.gl/), the facade textures were heuristically generated (thus the similarity to op).