improve rendering speed by caching LevelGeometry in database

src/c3nav/mapdata/render/base.py

@@ -0,0 +1,50 @@
+import pickle
+
+from django.db import transaction
+from django.db.models import Q
+from shapely.ops import unary_union
+
+from c3nav.mapdata.models import Level
+
+
+class LevelGeometries:
+    def __init__(self):
+        self.altitudeareas = []
+        self.walls = None
+        self.doors = None
+
+    @staticmethod
+    def rebuild():
+        levels = Level.objects.prefetch_related('altitudeareas', 'buildings', 'doors', 'spaces',
+                                                'spaces__holes', 'spaces__columns')
+        for level in levels:
+            geoms = LevelGeometries()
+            buildings_geom = unary_union([b.geometry for b in level.buildings.all()])
+
+            for space in level.spaces.all():
+                if space.outside:
+                    space.geometry = space.geometry.difference(buildings_geom)
+                space.geometry = space.geometry.difference(unary_union([c.geometry for c in space.columns.all()]))
+                space.holes_geom = unary_union([h.geometry for h in space.holes.all()])
+                space.walkable_geom = space.geometry.difference(space.holes_geom)
+
+            spaces_geom = unary_union([s.geometry for s in level.spaces.all()])
+            geoms.doors = unary_union([d.geometry for d in level.doors.all()])
+            walkable_geom = unary_union([s.walkable_geom for s in level.spaces.all()]).union(geoms.doors)
+
+            for altitudearea in level.altitudeareas.all():
+                geoms.altitudeareas.append((altitudearea.geometry.intersection(walkable_geom), altitudearea.altitude))
+
+            geoms.walls = buildings_geom.difference(spaces_geom).difference(geoms.doors)
+            level.geoms_cache = pickle.dumps(geoms)
+            level.save()
+
+        with transaction.atomic():
+            for level in levels:
+                level.save()
+
+
+def get_render_level_data(level):
+    levels = Level.objects.filter(Q(on_top_of=level.pk) | Q(base_altitude__lte=level.base_altitude))
+    levels = levels.values_list('geoms_cache', 'default_height')
+    return levels