Utils/data_processing/camera/generate_static_cameras.py

"""Generate managed static CineCamera actors around BP_CameraTrajectory.

Run this file with Unreal Engine's Python interpreter while the target level is
open in the editor. Only actors named ``CineCamera_<integer>`` are replaced.
Other CineCamera actors are never deleted.
"""

from __future__ import annotations

import argparse
import hashlib
import math
import random
import re

import unreal


CONFIG_ACTOR_LABEL = "BP_CameraTrajectory"
MANAGED_CAMERA_PATTERN = re.compile(r"^CineCamera_\d+$")


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Generate PhysInOne static cameras.")
    parser.add_argument("--focal", type=float, default=18.0, help="Focal length in mm.")
    parser.add_argument("--aperture", type=float, default=10.0)
    parser.add_argument("--radius", type=float, default=100.0, help="Base radius in cm.")
    parser.add_argument("--min-latitude", type=float, default=30.0)
    parser.add_argument("--max-latitude", type=float, default=60.0)
    parser.add_argument(
        "--deterministic",
        action="store_true",
        help="Disable the stable level-specific longitude offset.",
    )
    return parser.parse_known_args()[0]


def find_config_actor():
    for actor in unreal.EditorLevelLibrary.get_all_level_actors():
        if actor.get_actor_label() == CONFIG_ACTOR_LABEL:
            return actor
    return None


def validate_config(config_actor, minimum_latitude: float, maximum_latitude: float) -> None:
    if not 0 <= minimum_latitude < maximum_latitude <= 90:
        raise ValueError("Latitude limits must satisfy 0 <= min < max <= 90.")

    scale = config_actor.get_actor_scale3d()
    rotation = config_actor.get_actor_rotation()
    tolerance = 1e-4
    if max(abs(rotation.roll), abs(rotation.pitch), abs(rotation.yaw)) > tolerance:
        raise ValueError("BP_CameraTrajectory rotation must be zero.")
    if max(abs(scale.x - scale.y), abs(scale.x - scale.z)) > tolerance:
        raise ValueError("BP_CameraTrajectory XYZ scale must be uniform.")
    if min(scale.x, scale.y, scale.z) <= 0:
        raise ValueError("BP_CameraTrajectory scale must be positive.")


def stable_seed(text: str) -> int:
    return int.from_bytes(hashlib.sha256(text.encode("utf-8")).digest()[:8], "big")


def remove_managed_static_cameras() -> int:
    removed = 0
    for actor in unreal.EditorLevelLibrary.get_all_level_actors():
        if isinstance(actor, unreal.CineCameraActor) and MANAGED_CAMERA_PATTERN.fullmatch(
            actor.get_actor_label()
        ):
            unreal.EditorLevelLibrary.destroy_actor(actor)
            removed += 1
    return removed


def configure_camera(camera_actor, focal: float, aperture: float) -> None:
    component = camera_actor.get_cine_camera_component()
    component.set_editor_property("current_focal_length", focal)
    component.set_editor_property("current_aperture", aperture)
    filmback = component.get_editor_property("filmback")
    filmback.sensor_width = 23.76
    filmback.sensor_height = 23.76
    component.set_editor_property("filmback", filmback)


def generate(args: argparse.Namespace) -> int:
    config_actor = find_config_actor()
    if config_actor is None:
        raise RuntimeError(f"Actor {CONFIG_ACTOR_LABEL!r} was not found in the current level.")
    validate_config(config_actor, args.min_latitude, args.max_latitude)

    count = int(config_actor.get_editor_property("Num"))
    if count < 1:
        raise ValueError("BP_CameraTrajectory.Num must be at least 1.")

    world = unreal.EditorLevelLibrary.get_editor_world()
    level_name = world.get_name()
    rng = random.Random(stable_seed(level_name))
    longitude_offset = 0.0 if args.deterministic else rng.uniform(0.0, 2.0 * math.pi)

    random_hemisphere = bool(config_actor.get_editor_property("RandomHemisphere"))
    upper_hemisphere = bool(config_actor.get_editor_property("UpperHemisphere"))
    if random_hemisphere:
        upper_hemisphere = rng.choice([True, False])

    removed = remove_managed_static_cameras()
    unreal.log(f"Removed {removed} managed static camera(s).")

    center = config_actor.get_actor_location()
    scale = config_actor.get_actor_scale3d()
    editor = unreal.EditorLevelLibrary()

    phi_min = math.radians(90.0 - args.max_latitude)
    phi_max = math.radians(90.0 - args.min_latitude)
    cos_min = math.cos(phi_min)
    cos_max = math.cos(phi_max)

    for index in range(count):
        fraction = (index + 0.5) / count
        phi = math.acos(cos_min + (cos_max - cos_min) * fraction)
        theta = math.pi * (1.0 + math.sqrt(5.0)) * (index + 0.5) + longitude_offset

        z_sign = 1.0 if upper_hemisphere else -1.0
        x = args.radius * math.sin(phi) * math.cos(theta) * scale.x
        y = args.radius * math.sin(phi) * math.sin(theta) * scale.y
        z = z_sign * args.radius * math.cos(phi) * scale.z
        location = unreal.Vector(center.x + x, center.y + y, center.z + z)

        direction = center - location
        rotation = unreal.MathLibrary.make_rot_from_x(unreal.MathLibrary.normal(direction))
        rotation.roll = 0.0
        camera = editor.spawn_actor_from_class(unreal.CineCameraActor, location, rotation)
        camera.set_actor_label(f"CineCamera_{index}")
        configure_camera(camera, args.focal, args.aperture)
        camera.attach_to_actor(
            config_actor,
            socket_name=unreal.Name(""),
            location_rule=unreal.AttachmentRule.KEEP_WORLD,
            rotation_rule=unreal.AttachmentRule.KEEP_WORLD,
            scale_rule=unreal.AttachmentRule.KEEP_WORLD,
            weld_simulated_bodies=True,
        )

    unreal.log(
        f"Generated {count} static camera(s) for {level_name}; "
        f"hemisphere={'upper' if upper_hemisphere else 'lower'}."
    )
    return count


if __name__ == "__main__":
    try:
        generate(parse_args())
    except Exception as exc:
        unreal.log_error(f"Static camera generation failed: {exc}")
        raise