3b1b-manim/manimlib/extract_scene.py

import inspect
import sys
import copy

from manimlib.scene.scene import Scene
from manimlib.config import get_custom_config
from manimlib.logger import log


class BlankScene(Scene):
    def construct(self):
        exec(get_custom_config()["universal_import_line"])
        self.embed()


def is_child_scene(obj, module):
    if not inspect.isclass(obj):
        return False
    if not issubclass(obj, Scene):
        return False
    if obj == Scene:
        return False
    if not obj.__module__.startswith(module.__name__):
        return False
    return True


def prompt_user_for_choice(scene_classes):
    name_to_class = {}
    max_digits = len(str(len(scene_classes)))
    for idx, scene_class in enumerate(scene_classes, start=1):
        name = scene_class.__name__
        print(f"{str(idx).zfill(max_digits)}: {name}")
        name_to_class[name] = scene_class
    try:
        user_input = input(
            "\nThat module has multiple scenes, "
            "which ones would you like to render?"
            "\nScene Name or Number: "
        )
        return [
            name_to_class[split_str] if not split_str.isnumeric() else scene_classes[int(split_str) - 1]
            for split_str in user_input.replace(" ", "").split(",")
        ]
    except IndexError:
        log.error("Invalid scene number")
        sys.exit(2)
    except KeyError:
        log.error("Invalid scene name")
        sys.exit(2)
    except EOFError:
        sys.exit(1)


def get_scene_config(config):
    return dict([
        (key, config[key])
        for key in [
            "window_config",
            "camera_config",
            "file_writer_config",
            "skip_animations",
            "start_at_animation_number",
            "end_at_animation_number",
            "leave_progress_bars",
            "preview",
            "presenter_mode",
        ]
    ])


def compute_total_frames(scene_class, scene_config):
    """
    When a scene is being written to file, a copy of the scene is run with
    skip_animations set to true so as to count how many frames it will require.
    This allows for a total progress bar on rendering, and also allows runtime
    errors to be exposed preemptively for long running scenes. The final frame
    is saved by default, so that one can more quickly check that the last frame
    looks as expected.
    """
    pre_config = copy.deepcopy(scene_config)
    pre_config["file_writer_config"]["write_to_movie"] = False
    pre_config["file_writer_config"]["save_last_frame"] = True
    pre_config["file_writer_config"]["quiet"] = True
    pre_config["skip_animations"] = True
    pre_scene = scene_class(**pre_config)
    pre_scene.run()
    total_time = pre_scene.time - pre_scene.skip_time
    return int(total_time * scene_config["camera_config"]["frame_rate"])


def get_scenes_to_render(scene_classes, scene_config, config):
    if config["write_all"]:
        return [sc(**scene_config) for sc in scene_classes]

    result = []
    for scene_name in config["scene_names"]:
        found = False
        for scene_class in scene_classes:
            if scene_class.__name__ == scene_name:
                fw_config = scene_config["file_writer_config"]
                if fw_config["write_to_movie"]:
                    fw_config["total_frames"] = compute_total_frames(scene_class, scene_config)
                scene = scene_class(**scene_config)
                result.append(scene)
                found = True
                break
        if not found and (scene_name != ""):
            log.error(f"No scene named {scene_name} found")
    if result:
        return result
    if len(scene_classes) == 1:
        result = [scene_classes[0]]
    else:
        result = prompt_user_for_choice(scene_classes)
    return [scene_class(**scene_config) for scene_class in result]


def get_scene_classes_from_module(module):
    if hasattr(module, "SCENES_IN_ORDER"):
        return module.SCENES_IN_ORDER
    else:
        return [
            member[1]
            for member in inspect.getmembers(
                module,
                lambda x: is_child_scene(x, module)
            )
        ]


def main(config):
    module = config["module"]
    scene_config = get_scene_config(config)
    if module is None:
        # If no module was passed in, just play the blank scene
        return [BlankScene(**scene_config)]

    all_scene_classes = get_scene_classes_from_module(module)
    scenes = get_scenes_to_render(all_scene_classes, scene_config, config)
    return scenes