Constructor arguments
How positional and keyword arguments are taken: radius, side length, coordinates, vectors, control points, and VGroup's variadic arguments.
This page lists 14 examples. The code is imported from corpus/examples/ctor/; the screenshots are end states rendered on real machines.
Circle positional argument (radius)
Two circles given only a radius differ in size; the radius values match the picture.
py
"""Circle 位置参数（半径）
@expect 两个只给半径位置参数的圆大小不同，半径值与画面一致。
@note CE 里 Circle(1.5) 比 Circle(radius=1.5) 更常见
"""
from manim import *
class CirclePositionalScene(Scene):
def construct(self):
# 第一个位置参数就是半径：1.5 与 0.8 两个圆大小不同
circle_big = Circle(1.5, color=BLUE).shift(LEFT * 3.2)
circle_small = Circle(0.8, color=GREEN).shift(RIGHT * 3.2)
label_big = Text("r = 1.5", font_size=28, color=BLUE)
label_big.move_to([-3.2, -2.6, 0])
label_small = Text("r = 0.8", font_size=28, color=GREEN)
label_small.move_to([3.2, -2.6, 0])
self.play(Create(circle_big), Write(label_big),
Create(circle_small), Write(label_small))
self.wait(0.3)Square positional argument (side length)
Two squares given only a side length differ in size.
py
"""Square 位置参数（边长）
@expect 两个只给边长位置参数的方块大小不同。"""
from manim import *
class SquarePositionalScene(Scene):
def construct(self):
# 第一个位置参数就是边长：2 与 1 两个方块大小不同
square_big = Square(2, color=YELLOW).shift(LEFT * 3.2)
square_small = Square(1, color=PINK).shift(RIGHT * 3.2)
label_big = Text("边长 = 2", font_size=28, color=YELLOW)
label_big.move_to([-3.2, -2.6, 0])
label_small = Text("边长 = 1", font_size=28, color=PINK)
label_small.move_to([3.2, -2.6, 0])
self.play(Create(square_big), Write(label_big),
Create(square_small), Write(label_small))
self.wait(0.3)Dot positional argument (coordinates)
The dot lands at the given coordinates, not at the default origin.
py
"""Dot 位置参数（坐标）
@expect 点落在传入的坐标处，不在默认原点。"""
from manim import *
class DotPositionalScene(Scene):
def construct(self):
dot = Dot([1.5, 1, 0], color=RED)
# 原点灰点 + 从原点连到红点的虚线 + 坐标标注：红点确实落在 (1.5, 1) 而非原点
origin = Dot(ORIGIN, color=GREY)
guide = DashedLine(ORIGIN, [1.5, 1, 0], color=GREY)
label = Text("(1.5, 1)", font_size=26)
label.move_to([2.45, 1.0, 0])
self.play(GrowFromCenter(dot), FadeIn(origin), Create(guide), Write(label))
self.wait(0.3)Text weight, style and size
Several Text runs differ visibly in weight, italics and font size.
py
"""Text 字重、字形与字号
@expect 几段 Text 的字重 / 斜体 / 字号差异肉眼可见。
@note CE 的 weight / slant 在 manim-web 里叫 fontWeight / fontStyle（camel 推不出来）
"""
from manim import *
class TextKwargsScene(Scene):
def construct(self):
title = Text("粗体标题", font_size=56, weight=BOLD, color=YELLOW)
note = Text("斜体说明", font_size=32, slant=ITALIC)
note.shift(DOWN * 1.5)
self.play(Write(title), FadeIn(note))
self.wait(0.3)Vector positional argument
One arrow whose direction and length match the vector passed in.
py
"""Vector 位置参数
@expect 一支箭头，方向与长度和传入的向量一致。
@note 2026-10-09 事故：Vector([...]) 当时报「位置参数暂不支持」
"""
from manim import *
class VectorScene(Scene):
def construct(self):
vec = Vector([2, 1, 0], color=TEAL)
# 原点灰点 + 水平/垂直虚线勾出两个分量：方向与长度确实就是 (2, 1)
origin = Dot(ORIGIN, color=GREY)
along_x = DashedLine(ORIGIN, [2, 0, 0], color=GREY)
along_y = DashedLine([2, 0, 0], [2, 1, 0], color=GREY)
label = Text("(2, 1)", font_size=26)
label.move_to([2.6, 1.3, 0])
self.play(GrowArrow(vec), FadeIn(origin), Create(along_x), Create(along_y), Write(label))
self.wait(0.3)ParametricFunction positional argument
A curve drawn from the parametric equations; the shape matches them (neither a circle nor a line).
py
"""ParametricFunction 位置参数
@expect 按参数方程画出的曲线，形状与参数方程一致（不是圆也不是直线）。
@note 2026-10-09 事故：同上报「位置参数暂不支持」；func 是 Python 函数
"""
from manim import *
class ParametricScene(Scene):
def construct(self):
curve = ParametricFunction(lambda t: [t, np.sin(t), 0], t_range=[-3, 3, 0.2], color=PURPLE)
self.play(Create(curve))
self.wait(0.3)FunctionGraph takes a function
The curve's shape matches the function passed in.
py
"""FunctionGraph 收函数
@expect 曲线形状与传入的函数一致。
@note CE 关键字叫 function，manim-web 叫 func（表里有 rename）
"""
from manim import *
class FunctionGraphScene(Scene):
def construct(self):
ax = Axes(x_range=[-3, 3, 1], y_range=[-1, 2, 1])
graph = FunctionGraph(func=lambda x: np.sin(x), x_range=[-3, 3], color=YELLOW)
self.play(Create(ax), Create(graph))
self.wait(0.3)RightAngle takes two lines
A right-angle mark (a small elbow) stands at the intersection of the two lines.
py
"""RightAngle 收两条线
@expect 直角记号（小折角）立在两条线相交的角上。
@note 2026-10-09 事故：两个错叠在一起——位置参数未登记 + line1 句柄没解析（getStart is not a function）
"""
from manim import *
class RightAngleScene(Scene):
def construct(self):
line1 = Line(start=[-2, -1, 0], end=[0, -1, 0])
line2 = Line(start=[0, -1, 0], end=[0, 1, 0])
right = RightAngle(line1, line2, length=0.4)
self.add(line1, line2)
self.play(Create(right))
self.wait(0.3)Angle takes three points
The arc opens across the angle determined by the three points; its opening matches the angle.
py
"""Angle 收三个点
@expect 圆弧贴着三个点确定的角张開，弧的开口与角一致。"""
from manim import *
class AnglePointsScene(Scene):
def construct(self):
# 三个点：A 是顶点，B、C 张开角的两条边；把点画出来才能核对「弧贴着角」
a = [-2.5, -1.5, 0]
b = [1.5, -1.5, 0]
c = [0.0, 1.4, 0]
line_ab = Line(a, b, color=GREY)
line_ac = Line(a, c, color=GREY)
# 三点定角：中间那个点是顶点（与 CE from_three_points 一致），故把 A 放中间
angle = Angle([b, a, c], radius=0.7, color=YELLOW)
dot_a = Dot(a, color=RED)
dot_b = Dot(b, color=RED)
dot_c = Dot(c, color=RED)
label_a = Text("A", font_size=28, color=RED).next_to(dot_a, DL, buff=0.15)
label_b = Text("B", font_size=28, color=RED).next_to(dot_b, DOWN, buff=0.15)
label_c = Text("C", font_size=28, color=RED).next_to(dot_c, UP, buff=0.15)
self.play(Create(line_ab), Create(line_ac), Create(angle),
FadeIn(dot_a), FadeIn(dot_b), FadeIn(dot_c),
Write(label_a), Write(label_b), Write(label_c))
self.wait(0.3)Brace takes one mobject
A brace hugs one side of the mobject, its length matching the mobject.
py
"""Brace 收一个物体
@expect 花括号贴在物体一侧，长短与物体相当。
@note 2026-10-09 事故：报错文案把 AI 推去写 Brace(mobject=...)，结果整个 kwargs 被当成首个位置参数
"""
from manim import *
class BraceScene(Scene):
def construct(self):
square = Square(side_length=1.6)
brace = Brace(square, buff=0.2)
label = brace.get_text("1.6")
self.play(Create(square), GrowFromCenter(brace))
self.play(Write(label))
self.wait(0.3)BraceBetweenPoints takes two points
A brace spans the two points, aligned with their connecting line and scaled to their distance.
py
"""BraceBetweenPoints 收两点
@expect 花括号撑在两点之间，方向与两点连线一致、长短与距离相称。"""
from manim import *
class BraceBetweenScene(Scene):
def construct(self):
brace = BraceBetweenPoints([-2, 0, 0], [2, 0, 0], color=YELLOW)
# 两端的灰点钉住括号撑开的位置，标注写明区间
ends = VGroup(Dot([-2, 0, 0], color=GREY), Dot([2, 0, 0], color=GREY))
label = Text("(-2,0) → (2,0)", font_size=26)
label.move_to([0, -1.6, 0])
self.play(GrowFromCenter(brace), FadeIn(ends), Write(label))
self.wait(0.3)CubicBezier takes four points
The curve follows a cubic Bézier through the four control points, with its endpoints on the first and fourth.
py
"""CubicBezier 收四个点
@expect 曲线按四个控制点走出三次贝塞尔的形状（起终点在第一、四个点上）。"""
from manim import *
class CubicBezierScene(Scene):
def construct(self):
points = [[-3, -1, 0], [-1, 1.5, 0], [1, -1.5, 0], [3, 1, 0]]
bezier = CubicBezier(*points, color=TEAL)
# 四颗灰色控制点 + 虚线控制多边形：曲线起终点压在第一、四颗点上
dots = VGroup(*[Dot(p, color=GREY, radius=0.08) for p in points])
hull = VGroup(
DashedLine(points[0], points[1], color=GREY),
DashedLine(points[1], points[2], color=GREY),
DashedLine(points[2], points[3], color=GREY),
)
self.play(Create(bezier), Create(hull), FadeIn(dots))
self.wait(0.3)ValueTracker takes an initial value
ValueTracker draws nothing (it is only a number); the scene renders without error and the other mobjects behave.
py
"""ValueTracker 收一个初值
@expect ValueTracker 不画任何东西（它只是数值），场景渲染不炸、其余物体正常。"""
from manim import *
class ValueTrackerScene(Scene):
def construct(self):
tracker = ValueTracker(0)
dot = Dot(point=[-2, 0, 0], color=RED)
dot.add_updater(lambda m: m.move_to([tracker.get_value() - 2, 0, 0]))
self.add(tracker, dot)
self.play(tracker.animate.set_value(4), run_time=1)
self.wait(0.3)VGroup variadic positional arguments
Several mobjects gathered into one VGroup move as a whole; their relative positions stay fixed.
py
"""VGroup 变长位置参数
@expect 若干物体收进一个 VGroup 后整体定位：一起移动、相对位置不变。"""
from manim import *
class VgroupVariadicScene(Scene):
def construct(self):
group = VGroup(Circle(radius=0.6), Square(side_length=1), Triangle())
group.arrange(RIGHT, buff=0.6)
# ghost 用同字面量重建、同样 arrange（整组 copy / 非字面量 VGroup 都会丢位置）：
# 移位后 ghost 留在原位，衬出「整组一起动、相对位置不变」
ghost = VGroup(Circle(radius=0.6), Square(side_length=1), Triangle())
ghost.arrange(RIGHT, buff=0.6)
ghost.set_opacity(0.3)
self.play(Create(group))
group.shift(UP * 1.2)
self.add(ghost)
self.wait(0.3)