Manim Vector Field

The vector field VMobject object in Manim is defined in vector_field.py.

Codes in Vector_field.py

Available codes defined in manimlib.mobject.vector_field.py

Four classes, VectorField(VGroup), StreamLines(VGroup), ShowPassingFlashWithThinningStrokeWidth(AnimationGroup) and AnimatedStreamLines(VGroup) are defined.

Import

import numpy as np
import os
import itertools as it
from PIL import Image
import random

from manimlib.constants import *

from manimlib.animation.composition import AnimationGroup
from manimlib.animation.indication import ShowPassingFlash
from manimlib.mobject.geometry import Vector
from manimlib.mobject.types.vectorized_mobject import VGroup
from manimlib.mobject.types.vectorized_mobject import VMobject
from manimlib.utils.bezier import inverse_interpolate
from manimlib.utils.bezier import interpolate
from manimlib.utils.color import color_to_rgb
from manimlib.utils.color import rgb_to_color
from manimlib.utils.config_ops import digest_config
from manimlib.utils.rate_functions import linear
from manimlib.utils.simple_functions import sigmoid
from manimlib.utils.space_ops import get_norm
# from manimlib.utils.space_ops import normalize

Constant

DEFAULT_SCALAR_FIELD_COLORS = [BLUE_E, GREEN, YELLOW, RED]

Function Front

• def get_colored_background_image(scalar_field_func, number_to_rgb_func, pixel_height=DEFAULT_PIXEL_HEIGHT, pixel_width=DEFAULT_PIXEL_WIDTH)
• def get_rgb_gradient_function(min_value=0, max_value=1, colors=[BLUE, RED], flip_alphas=True, # Why? )
  • def func(values)
• def get_color_field_image_file(scalar_func, min_value=0, max_value=2, colors=DEFAULT_SCALAR_FIELD_COLORS )
• def move_along_vector_field(mobject, func)
• def move_submobjects_along_vector_field(mobject, func)
  • def apply_nudge(mob, dt)
• def move_points_along_vector_field(mobject, func)
  • def apply_nudge(self, dt)

Class VectorField(VGroup)

class manimlib.mobject.vector_field.VectorField(VGroup)version 19Dec2019

Configuration

CONFIG = {
        "delta_x": 0.5,
        "delta_y": 0.5,
        "x_min": int(np.floor(-FRAME_WIDTH / 2)),
        "x_max": int(np.ceil(FRAME_WIDTH / 2)),
        "y_min": int(np.floor(-FRAME_HEIGHT / 2)),
        "y_max": int(np.ceil(FRAME_HEIGHT / 2)),
        "min_magnitude": 0,
        "max_magnitude": 2,
        "colors": DEFAULT_SCALAR_FIELD_COLORS,
        # Takes in actual norm, spits out displayed norm
        "length_func": lambda norm: 0.45 * sigmoid(norm),
        "opacity": 1.0,
        "vector_config": {},
    }

Functions

• def __init__(self, func, **kwargs)
• def get_vector(self, point, **kwargs)

Class StreamLines(VGroup)

class manimlib.mobject.vector_field.StreamLines(VGroup)version 19Dec2019

Configuration

    CONFIG = {
        # TODO, this is an awkward way to inherit
        # defaults to a method.
        "start_points_generator_config": {},
        # Config for choosing start points
        "x_min": -8,
        "x_max": 8,
        "y_min": -5,
        "y_max": 5,
        "delta_x": 0.5,
        "delta_y": 0.5,
        "n_repeats": 1,
        "noise_factor": None,
        # Config for drawing lines
        "dt": 0.05,
        "virtual_time": 3,
        "n_anchors_per_line": 100,
        "stroke_width": 1,
        "stroke_color": WHITE,
        "color_by_arc_length": True,
        # Min and max arc lengths meant to define
        # the color range, should color_by_arc_length be True
        "min_arc_length": 0,
        "max_arc_length": 12,
        "color_by_magnitude": False,
        # Min and max magnitudes meant to define
        # the color range, should color_by_magnitude be True
        "min_magnitude": 0.5,
        "max_magnitude": 1.5,
        "colors": DEFAULT_SCALAR_FIELD_COLORS,
        "cutoff_norm": 15,
    }

Functions

• def __init__(self, func, **kwargs)
• def get_start_points(self)

Class ShowPassingFlashWithThinningStrokeWidth(AnimationGroup)

class manimlib.mobject.vector_field.ShowPassingFlashWithThinningStrokeWidth(AnimationGroup)version 19Dec2019

Configuration

    CONFIG = {
        "n_segments": 10,
        "time_width": 0.1,
        "remover": True
    }

Functions

• def __init__(self, vmobject, **kwargs)

Class AnimatedStreamLines(VGroup)

class manimlib.mobject.vector_field.AnimatedStreamLines(VGroup)version 19Dec2019

Configuration

    CONFIG = {
        "lag_range": 4,
        "line_anim_class": ShowPassingFlash,
        "line_anim_config": {
            "run_time": 4,
            "rate_func": linear,
            "time_width": 0.3,
        },
    }

Functions

• def __init__(self, stream_lines, **kwargs)
• def update(self, dt)

Source and Reference

https://github.com/3b1b/manim19Dec2019