feat: add Cesium semantic inspection mode

blender/export_cesium.py

@@ -29,6 +29,16 @@ from osmassets.materials import CESIUM_EXPORT_PROPERTY, link_alpha_clip  # noqa:
 # mesh's shared slots can recognise its own output and leave it alone.
 EXPORT_PREFIX = "Cesium "
 
+# Top-level collections are the authoring scene's stable semantic boundary.
+# Their numeric prefixes are draw-order labels in Blender, not part of the
+# Cesium asset contract below.
+SEMANTIC_ASSETS = (
+    ("roads", "道路", ("03_Roads",)),
+    ("buildings", "建筑", ("04_Buildings",)),
+    ("vegetation", "绿化与设施", ("02_Green", "05_Props")),
+    ("water", "水体", ("01_Water",)),
+)
+
 # Fraction of its own albedo a cut-out foliage material emits, to keep the
 # shadowed side of a crown off Cesium's near-black ambient floor. Kept well
 # under the 0.18 the buildings use: a tree still has to read as lit from one
@@ -544,6 +554,54 @@ def triangulate_mesh(obj):
         obj.modifiers.remove(modifier)
 
 
+def export_glb(filepath, meshes):
+    """Export a prepared object subset without changing authoring visibility."""
+    bpy.ops.object.select_all(action="DESELECT")
+    for obj in meshes:
+        obj.select_set(True)
+    bpy.context.view_layer.objects.active = meshes[0] if meshes else None
+    os.makedirs(os.path.dirname(filepath), exist_ok=True)
+    bpy.ops.export_scene.gltf(
+        filepath=filepath,
+        export_format="GLB",
+        use_selection=True,
+        export_apply=False,
+        export_texcoords=True,
+        export_normals=True,
+        export_materials="EXPORT",
+        export_image_format="AUTO",
+        export_tangents=True,
+        export_extras=True,
+        export_cameras=False,
+        export_lights=False,
+    )
+
+
+def semantic_asset_specs(glb_path, meshes):
+    """Derive optional inspection assets from the scene's named collections."""
+    stem, extension = os.path.splitext(glb_path)
+    by_collection = {}
+    for collection in bpy.context.scene.collection.children:
+        by_collection[collection.name] = set(collection.all_objects)
+
+    specs = []
+    for asset_id, label, collection_names in SEMANTIC_ASSETS:
+        objects = set()
+        for name in collection_names:
+            objects.update(by_collection.get(name, set()))
+        subset = [obj for obj in meshes if obj in objects]
+        if not subset:
+            continue
+        path = stem + "-" + asset_id + extension
+        specs.append({
+            "id": asset_id,
+            "label": label,
+            "path": path,
+            "meshes": subset,
+        })
+    return specs
+
+
 def export(args):
     if not os.path.exists(args["blend"]):
         raise FileNotFoundError(args["blend"])
@@ -583,30 +641,10 @@ def export(args):
                 material_map[source.name] = make_export_material(source)
             slot.material = material_map[source.name]
 
-    bpy.ops.object.select_all(action="DESELECT")
-    for obj in meshes:
-        obj.select_set(True)
-    bpy.context.view_layer.objects.active = meshes[0] if meshes else None
-
-    os.makedirs(os.path.dirname(args["glb"]), exist_ok=True)
-    bpy.ops.export_scene.gltf(
-        filepath=args["glb"],
-        export_format="GLB",
-        use_selection=True,
-        export_apply=False,
-        export_texcoords=True,
-        export_normals=True,
-        export_materials="EXPORT",
-        export_image_format="AUTO",
-        # The foliage materials carry a normal map, and glTF leaves tangent
-        # derivation to the renderer when TANGENT is absent. On thin
-        # double-sided leaf cards that derivation is unreliable, so ship real
-        # tangents — it costs four floats a vertex on meshes this small.
-        export_tangents=True,
-        export_extras=True,
-        export_cameras=False,
-        export_lights=False,
-    )
+    export_glb(args["glb"], meshes)
+    semantic_assets = semantic_asset_specs(args["glb"], meshes)
+    for asset in semantic_assets:
+        export_glb(asset["path"], asset["meshes"])
 
     scene = bpy.context.scene
     try:
@@ -626,7 +664,14 @@ def export(args):
             "type": "model",
             "url": os.path.basename(args["glb"]),
             "enabled": True,
-        }],
+        }] + [{
+            "id": asset["id"],
+            "label": asset["label"],
+            "type": "model",
+            "url": os.path.basename(asset["path"]),
+            "enabled": False,
+            "category": "semantic",
+        } for asset in semantic_assets],
         "coordinate_system": "local ENU meters (X east, Y north, Z up)",
         "heading_correction_degrees": -90.0,
         "anchor": {"longitude": center_lon, "latitude": center_lat, "height": 0.35},
@@ -660,6 +705,7 @@ def export(args):
     print("CESIUM_EXPORT_DONE", json.dumps({
         "glb": args["glb"], "metadata": args["metadata"],
         "meshes": len(meshes), "materials": len(material_map),
+        "semantic_assets": [asset["id"] for asset in semantic_assets],
         "anchor": [center_lon, center_lat],
     }, ensure_ascii=True))