#!/usr/bin/env python3 """ citygml_to_cityjson.py — Convert Lyon CityGML (LOD2) to CityJSON v1.1 Handles lod2MultiSurface and lod2Solid geometries. Maps EPSG:3946 CRS. Creates stable building IDs. """ import json, os, sys, math, numpy as np from lxml import etree NSMAP = { 'gml': 'http://www.opengis.net/gml', 'bldg': 'http://www.opengis.net/citygml/building/2.0', } def _tag(elem): return etree.QName(elem).localname def _find_recursive(elem, local_name): for child in elem.iter(): if _tag(child) == local_name: return child return None def _parse_poslist(text): parts = text.strip().split() return [float(p) for p in parts] def _parse_polygon_patches(geom_elem): """Parse lod2MultiSurface → list of surfaces (each a list of [x,y,z] vertices).""" surfaces = [] for polygon_elem in geom_elem.iter(): if _tag(polygon_elem) == 'Polygon': exterior = _find_recursive(polygon_elem, 'exterior') if exterior is None: continue ring = _find_recursive(exterior, 'LinearRing') if ring is None: continue poslist = _find_recursive(ring, 'posList') if poslist is None: continue coords = _parse_poslist(poslist.text) verts = [[coords[i], coords[i+1], coords[i+2]] for i in range(0, len(coords)-2, 3)] if verts: surfaces.append(verts) return surfaces def _parse_solid(geom_elem): """Parse lod2Solid → list of surfaces.""" surfaces = [] for shell_elem in geom_elem.iter(): if _tag(shell_elem) in ('exterior', 'Shell'): for polygon_elem in shell_elem.iter(): if _tag(polygon_elem) == 'Polygon': exterior = _find_recursive(polygon_elem, 'exterior') if exterior is None: continue ring = _find_recursive(exterior, 'LinearRing') if ring is None: continue poslist = _find_recursive(ring, 'posList') if poslist is None: continue coords = _parse_poslist(poslist.text) verts = [[coords[i], coords[i+1], coords[i+2]] for i in range(0, len(coords)-2, 3)] if verts: surfaces.append(verts) return surfaces def _deduplicate_vertices(buildings): """Build global vertex array, remap surfaces to indices.""" vert_to_idx = {} vertices_list = [] for bid, bdata in buildings.items(): new_surfaces = [] for surface in bdata.get('surfaces', []): new_surf = [] for v in surface: key = (round(v[0], 6), round(v[1], 6), round(v[2], 6)) if key not in vert_to_idx: vert_to_idx[key] = len(vertices_list) vertices_list.append(v) new_surf.append(vert_to_idx[key]) new_surfaces.append([new_surf]) bdata['boundaries'] = new_surfaces del bdata['surfaces'] return vertices_list, buildings def _get_bbox(buildings): """Compute global bounding box from building surfaces.""" all_verts = [] for b in buildings.values(): for surf_list in b.get('boundaries', []): for surf in surf_list: for vidx in surf: pass # We'll compute from vertices directly later return None def convert_gml_to_cityjson(gml_path, year, arrondissement): """Convert one CityGML file to CityJSON dict.""" print(f" Parsing {os.path.basename(gml_path)}...") buildings = {} crs_uri = None current_building = None context = etree.iterparse(gml_path, events=('start', 'end'), huge_tree=True) for event, elem in context: tag = _tag(elem) if event == 'start': if tag == 'Building': gml_id = elem.get('{http://www.opengis.net/gml}id', f'unknown_{len(buildings)}') current_building = {'id': gml_id, 'surfaces': []} if tag in ('boundedBy', 'Envelope') and crs_uri is None: srs = elem.get('srsName', '') if srs: crs_uri = srs if event == 'end': if tag in ('lod2MultiSurface', 'lod2Solid') and current_building is not None: surfaces = _parse_polygon_patches(elem) if tag == 'lod2MultiSurface' else _parse_solid(elem) if surfaces: current_building['surfaces'].extend(surfaces) if tag == 'Building' and current_building is not None: if current_building['surfaces']: bid = f"{year}_{arrondissement}_{current_building['id']}" buildings[bid] = current_building current_building = None if tag not in ('Building', 'lod2MultiSurface', 'lod2Solid'): elem.clear() if not buildings: print(f" WARNING: No buildings extracted!") return None # Deduplicate vertices vertices, buildings = _deduplicate_vertices(buildings) # Compute global bounding box all_v = np.array(vertices) bbox = [float(all_v[:,0].min()), float(all_v[:,0].max()), float(all_v[:,1].min()), float(all_v[:,1].max()), float(all_v[:,2].min()), float(all_v[:,2].max())] # Transform for integer compression translate = [bbox[0], bbox[2], bbox[4]] max_dim = max(bbox[1]-bbox[0], bbox[3]-bbox[2], bbox[5]-bbox[4]) scale_factor = max(max_dim / 1e6, 1e-6) scale = [scale_factor, scale_factor, scale_factor] # Build CityObjects city_objects = {} for bid, bdata in buildings.items(): city_objects[bid] = { 'type': 'Building', 'geometry': [{ 'type': 'MultiSurface', 'lod': '2', 'boundaries': bdata['boundaries'], }], } cityjson = { 'type': 'CityJSON', 'version': '1.1', 'metadata': { 'referenceSystem': crs_uri or 'EPSG:3946', 'geographicalExtent': bbox, 'datasetTitle': f'Lyon {arrondissement} {year}', }, 'transform': {'scale': scale, 'translate': translate}, 'CityObjects': city_objects, 'vertices': vertices, } print(f" {len(city_objects)} buildings, {len(vertices)} vertices, CRS={crs_uri}") return cityjson def main(): base_dir = os.path.dirname(os.path.abspath(__file__)) lyon_data = os.path.join(base_dir, '..', 'data', 'lyon') years = ['2009', '2012', '2015'] for year in years: gml_dir = os.path.join(lyon_data, year) cityjson_dir = os.path.join(lyon_data, year + '_cityjson') os.makedirs(cityjson_dir, exist_ok=True) gml_files = sorted([f for f in os.listdir(gml_dir) if f.endswith('.gml')]) if not gml_files: print(f"No GML files found for {year}") continue print(f"\n{'='*60}") print(f"YEAR {year}: {len(gml_files)} files") for gml_file in gml_files: arr = gml_file.replace(f'_BATI_{year}.gml', '').replace('LYON_', '') gml_path = os.path.join(gml_dir, gml_file) output_path = os.path.join(cityjson_dir, f'LYON_{arr}_{year}.json') if os.path.exists(output_path): print(f" Skipping {gml_file} (already converted)") continue cityjson = convert_gml_to_cityjson(gml_path, year, arr) if cityjson: with open(output_path, 'w') as f: json.dump(cityjson, f) size_mb = os.path.getsize(output_path) / 1024 / 1024 print(f" → Saved: {os.path.basename(output_path)} ({size_mb:.1f} MB)") if __name__ == '__main__': main()