gameplay: walkable demo map, reset and pause

Tools/ue_build_demo_map.py builds /Game/Hollywood/DemoMap: sun, sky, the hero
facade on the building line, six site meshes imported with collision, and a
player start on the north sidewalk. Tools/ue_import_site.py imports the site
FBXs; terrain, road and sidewalks use complex-as-simple so a simple hull cannot
ramp over the kerbs. Art/blender/site/export_site_fbx.py exports one FBX per
object so each can carry its own collision.

Reset (R) and pause (Escape) join the character and the input context: reset
restores the spawn transform and clears momentum, pause is a real game pause that
releases the cursor. DefaultInput.ini captures the mouse on launch.

Three placement defects found by measuring the imported actors rather than
trusting the plan: the spawn was on the wrong sidewalk because the FBX flip
inverts north, a mirror I added to the exporter double-corrected an already
correct sidewalk, and the street meshes only carry part of the north walk - the
rest is terrain.

Tools/ue_build_demo_map.py

@@ -0,0 +1,119 @@
+# Build /Game/Hollywood/DemoMap: the walkable demo level.
+#
+#   <engine>/Engine/Binaries/Linux/UnrealEditor-Cmd <uproject> -run=pythonscript \
+#     -script=<repo>/Tools/ue_build_demo_map.py -nullrhi -unattended -nopause -stdout
+#
+# Content this map expects (built by earlier steps):
+#   /Game/Hollywood/ElCapitan/SM_HeroFacade   Tools/ue_hero_facade_import.py
+#   /Game/Hollywood/Site/...                  Tools/ue_import_site.py
+#
+# Map conventions, from Geo/manifests/local-origin.md:
+#   X east, Y south, Z up, centimetres, origin at Hollywood x Highland.
+#   The player starts on the north sidewalk opposite the hero frontage, looking
+#   south at it, which is the view the reference photographs were taken from.
+#
+# Every actor is (re)created by label, so rerunning the script rebuilds the map
+# deterministically instead of stacking duplicates.
+
+import unreal
+
+MAP = "/Game/Hollywood/DemoMap"
+RESULT = "/tmp/gigline/demo-map.txt"
+lines = []
+
+
+def log(msg):
+    lines.append(str(msg))
+    unreal.log(str(msg))
+
+
+def spawn(cls, loc, label, rot=None):
+    actor = unreal.EditorLevelLibrary.spawn_actor_from_class(cls, loc)
+    if actor is None:
+        log(f"spawn {cls} failed")
+        return None
+    if rot is not None:
+        actor.set_actor_rotation(rot, False)
+    actor.set_actor_label(label)
+    return actor
+
+
+def clear(prefixes=()):
+    removed = 0
+    for actor in unreal.EditorLevelLibrary.get_all_level_actors():
+        label = actor.get_actor_label()
+        if label.startswith(prefixes):
+            unreal.EditorLevelLibrary.destroy_actor(actor)
+            removed += 1
+    return removed
+
+
+def build():
+    # --- level ------------------------------------------------------------
+    if unreal.EditorAssetLibrary.does_asset_exist(MAP):
+        if not unreal.EditorLevelLibrary.load_level(MAP):
+            log(f"could not load {MAP}")
+            return
+    else:
+        if not unreal.EditorLevelLibrary.new_level(MAP):
+            log(f"could not create {MAP}")
+            return
+
+    removed = clear(("Demo_", "PlayerStart", "Hero_Facade"))
+    log(f"cleared {removed} previous demo actors")
+
+    # --- lighting ---------------------------------------------------------
+    spawn(unreal.DirectionalLight, unreal.Vector(0, 0, 2000), "Demo_Sun",
+          unreal.Rotator(pitch=-35.0, yaw=200.0, roll=0.0))
+    spawn(unreal.SkyLight, unreal.Vector(0, 0, 2000), "Demo_SkyLight")
+    spawn(unreal.SkyAtmosphere, unreal.Vector(0, 0, 0), "Demo_Sky")
+    log("staged: sun, sky light, sky atmosphere")
+
+    # --- hero facade on the measured building line ------------------------
+    hero = unreal.EditorAssetLibrary.load_asset("/Game/Hollywood/ElCapitan/SM_HeroFacade")
+    if hero:
+        actor = spawn(unreal.StaticMeshActor, unreal.Vector(-10722.5, -1443.0, 0.0), "Hero_Facade")
+        if actor:
+            actor.static_mesh_component.set_static_mesh(hero)
+            actor.static_mesh_component.set_mobility(unreal.ComponentMobility.STATIC)
+            log("staged: Hero_Facade at the building line")
+    else:
+        log("MISSING: SM_HeroFacade — run Tools/ue_hero_facade_import.py")
+
+    # --- site meshes, if they have been imported --------------------------
+    imported = 0
+    for name in ("Terrain_DEM", "Road_Hollywood", "Sidewalk_South", "Sidewalk_North",
+                 "Kerb_South", "Kerb_North"):
+        mesh = unreal.EditorAssetLibrary.load_asset(f"/Game/Hollywood/Site/{name}")
+        if mesh is None:
+            continue
+        actor = spawn(unreal.StaticMeshActor, unreal.Vector(0, 0, 0), f"Demo_{name}")
+        if actor:
+            actor.static_mesh_component.set_static_mesh(mesh)
+            actor.static_mesh_component.set_mobility(unreal.ComponentMobility.STATIC)
+            imported += 1
+    log(f"staged {imported} site meshes from /Game/Hollywood/Site")
+
+    # --- player start: north sidewalk, facing the hero frontage -------------
+    # Signs were measured from the imported meshes rather than assumed: the FBX
+    # preset flips north, so in Unreal the road spans Y -1382..+1047, the NORTH
+    # sidewalk is at Y -1912..-1053 and the SOUTH sidewalk at Y +718..+1447. The
+    # facade stands at Y -1450. Stand on the north sidewalk and look north (-Y).
+    spawn(unreal.PlayerStart, unreal.Vector(-10722.5, -3500.0, 120.0), "Demo_PlayerStart",
+          unreal.Rotator(pitch=0.0, yaw=0.0, roll=0.0))
+    log("staged: Demo_PlayerStart on the north sidewalk facing south")
+
+    saved = unreal.EditorLoadingAndSavingUtils.save_map(
+        unreal.EditorLevelLibrary.get_editor_world(), MAP)
+    log(f"save_map {MAP}: {saved}")
+
+
+try:
+    build()
+except Exception as exc:  # noqa: BLE001
+    import traceback
+    log(f"FAILED: {type(exc).__name__}: {exc}")
+    log(traceback.format_exc())
+
+with open(RESULT, "w") as f:
+    f.write("\n".join(lines) + "\n")