feat: first-person player with Enhanced Input

AGigLineCharacter: 1.75 m capsule, 1.60 m eye camera, 4 m/s walk, mouse look
scaled in degrees per second (no double DeltaTime), jump. Loaded ahead of a
Blueprint so the demo is playable with no assets wired by hand.

Tools/ue_create_input_assets.py builds /Game/Input headlessly: five 1D actions
and an 11-mapping context. One action per direction instead of per-key modifiers,
because modifier objects do not survive the save path here: a mapping's modifier
array serialises None, and dimensioning a 2D move with per-key axis masks would
need exactly those modifiers. The cost is four action assets rather than two.

Also adds a fourth review camera at eye height and documents it; its approval is
pending.

Tools/ue_build_review_map.py

@@ -100,6 +100,9 @@ try:
             unreal.Vector(900, -1100, 500),
             unreal.Vector(200, -300, 160),
             unreal.Vector(200, 100, 200),
+            # first-person eye height, just south-east of the character: this is the
+            # view a player has at spawn, capsule and camera stack in frame
+            unreal.Vector(120, -260, 165),
         ])
         shots.set_editor_property("shot_rotations", [
             unreal.MathLibrary.find_look_at_rotation(
@@ -108,10 +111,13 @@ try:
                 unreal.Vector(200, -300, 160), unreal.Vector(0, 0, 85)),
             unreal.MathLibrary.find_look_at_rotation(
                 unreal.Vector(200, 100, 200), unreal.Vector(0, 600, 50)),
+            unreal.MathLibrary.find_look_at_rotation(
+                unreal.Vector(120, -260, 165), unreal.Vector(-200, 600, 90)),
         ])
-        shots.set_editor_property("shot_names", ["overview", "character", "scale-cubes"])
+        shots.set_editor_property("shot_names",
+                                  ["overview", "character", "scale-cubes", "first-person"])
         shots.set_editor_property("quit_when_done", True)
-        log("staged: ShotSequencer with 3 cameras")
+        log("staged: ShotSequencer with 4 cameras")
 except Exception as exc:  # noqa
     log(f"staging failed: {exc!r}")
 

Tools/ue_create_input_assets.py

@@ -0,0 +1,156 @@
+# Creates the Enhanced Input assets the first-person character loads:
+#   /Game/Input/IA_Move     Axis2D, WASD + left stick
+#   /Game/Input/IA_Look     Axis2D, mouse XY + right stick
+#   /Game/Input/IA_Jump     axis1d, Space / gamepad face button
+#   /Game/Input/IMC_Default InputMappingContext holding the three mappings
+#
+# Run headless (imports/dirty packages are saved before exit):
+#   <engine>/Engine/Binaries/Linux/UnrealEditor-Cmd <uproject> -run=pythonscript \
+#     -script=<repo>/Tools/ue_create_input_assets.py -nullrhi -unattended -nopause \
+#     -stdout -FullStdOutLogOutput
+#
+# The result goes to /tmp/gigline/input-assets.txt because 5.8's pythonscript
+# commandlet swallows print() output with -stdout.
+#
+# Mapping choices:
+#   - Look stays unit-free (no scalar modifier): the character applies its own
+#     degrees-per-second, and a modifier here would double-scale.
+#   - Move is a 2D axis: W = +Y, S = -Y, D = +X, A = -X via Negate on the Y axis.
+#     For keyboard keys the Negate modifier's Y axis maps to the axis's Y.
+
+import unreal
+
+ASSET_DIR = "/Game/Input"
+_KEEP_ALIVE = []
+
+
+def negate_y_modifier():
+    """A negate-by-Y modifier, built with its Y flag set and X/Z cleared.
+
+    Returns the object plus its falsy reference; constructing the default
+    modifier gives all axes true, so each flag is set explicitly. The caller owns
+    keep-alive.
+    """
+    neg = unreal.InputModifierNegate()
+    neg.set_editor_property("x", False)
+    neg.set_editor_property("y", True)
+    neg.set_editor_property("z", False)
+    return neg
+RESULT = "/tmp/gigline/input-assets.txt"
+lines = []
+
+
+def log(msg):
+    lines.append(str(msg))
+    unreal.log(str(msg))
+
+
+def fresh(name, cls, factory):
+    """Load the asset if it exists, otherwise create it.
+
+    Deleting then recreating in the same commandlet run fails: create_asset
+    returns None for a path deleted earlier in the process. Overwriting in place
+    is also what keeps the assets' identities stable across reruns.
+    """
+    path = f"{ASSET_DIR}/{name}"
+    existing = unreal.EditorAssetLibrary.load_asset(path)
+    if existing is not None:
+        return existing
+    return unreal.AssetToolsHelpers.get_asset_tools().create_asset(
+        name, ASSET_DIR, cls, factory())
+
+
+def save(asset):
+    unreal.EditorAssetLibrary.save_loaded_asset(asset, only_if_is_dirty=False)
+
+
+def make_key(name):
+    """Build an FKey by name.
+
+    `unreal.InputCoreTypes` is not exposed to Python in 5.8 and `unreal.Key` does
+    not accept a constructor argument, but the struct's `import_text` parses the
+    key's export text, which is just its name.
+    """
+    key = unreal.Key()
+    key.import_text(name)
+    return key
+
+
+def build():
+    if not unreal.EditorAssetLibrary.does_directory_exist(ASSET_DIR):
+        unreal.EditorAssetLibrary.make_directory(ASSET_DIR)
+
+    # --- actions ---------------------------------------------------------
+    # Move keys are one-dimensional: W/S carry forward/back on the value's single
+    # component and D/A carry strafe, combined by the character. A 2D value would
+    # need per-key axis modifiers, and modifiers do not survive the save path here.
+    ia_move = fresh("IA_Move", unreal.InputAction, unreal.InputAction_Factory)
+    ia_move.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
+    save(ia_move)
+
+    ia_look = fresh("IA_Look", unreal.InputAction, unreal.InputAction_Factory)
+    ia_look.set_editor_property("value_type", unreal.InputActionValueType.AXIS2D)
+    save(ia_look)
+
+    ia_jump = fresh("IA_Jump", unreal.InputAction, unreal.InputAction_Factory)
+    ia_jump.set_editor_property("value_type", unreal.InputActionValueType.BOOLEAN)
+    save(ia_jump)
+
+    # --- mapping context -------------------------------------------------
+    imc = fresh("IMC_Default", unreal.InputMappingContext, unreal.InputMappingContext_Factory)
+
+    # Nine entries, one per key. No modifiers: the character negates S and A in
+    # C++ instead, because a modifier object attached to a mapping struct
+    # serialises as None on save in this build (the struct's object array does not
+    # keep the modifier alive across the save path). One less moving part, and the
+    # negation is visible where it is used.
+    # Two actions feed the one-dimensional move: IA_Move for forward/back, and a
+    # second action for strafe, both reporting on the value's single component.
+    ia_strafe = fresh("IA_Strafe", unreal.InputAction, unreal.InputAction_Factory)
+    ia_strafe.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
+    save(ia_strafe)
+
+    ia_back = fresh("IA_MoveBack", unreal.InputAction, unreal.InputAction_Factory)
+    ia_back.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
+    save(ia_back)
+
+    ia_left = fresh("IA_StrafeLeft", unreal.InputAction, unreal.InputAction_Factory)
+    ia_left.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
+    save(ia_left)
+
+    mapping_table = [
+        (ia_move, "W"), (ia_back, "S"), (ia_strafe, "D"), (ia_left, "A"),
+        (ia_move, "Gamepad_LeftY"), (ia_strafe, "Gamepad_LeftX"),
+        (ia_look, "MouseX"), (ia_look, "MouseY"), (ia_look, "Gamepad_Right2D"),
+        (ia_jump, "SpaceBar"), (ia_jump, "Gamepad_FaceButton_Bottom"),
+    ]
+
+    mappings = []
+    for action, key_name in mapping_table:
+        try:
+            entry = unreal.EnhancedActionKeyMapping()
+            entry.set_editor_property("action", action)
+            entry.set_editor_property("key", make_key(key_name))
+            mappings.append(entry)
+        except Exception as exc:  # noqa: BLE001
+            log(f"skip {action.get_name()}/{key_name}: {exc}")
+
+    # Array property: rebuild it rather than mutating in place.
+    imc.set_editor_property("mappings", mappings)
+    save(imc)
+
+    log(f"IA_Move={ia_move.get_path_name()} IA_Look={ia_look.get_path_name()} "
+        f"IA_Jump={ia_jump.get_path_name()}")
+    log(f"IMC_Default={imc.get_path_name()} mappings={len(mappings)}")
+    log("assets=" + ",".join(unreal.EditorAssetLibrary.list_assets(ASSET_DIR)))
+
+
+try:
+    build()
+except Exception as exc:  # noqa: BLE001 - surface the failure in the result file
+    import traceback
+    log(f"FAILED: {type(exc).__name__}: {exc}")
+    log(traceback.format_exc())
+
+with open(RESULT, "w") as handle:
+    handle.write("\n".join(lines))