如何使用manim创建正确的饼图
无论如何，我正在尝试（这实际上是我的第一个manim程序）。
from manim import *
import copy
import numpy as np
import random
color_palette = [BLUE, GREEN, YELLOW, GREY_BROWN]
class TestPie(Scene):
def construct(self):
n_elements = 3
radius = 1
weights = np.random.rand(n_elements)
weights /= weights.sum()
angles = weights*np.pi*2
angles_offset = [0]+np.cumsum(weights*np.pi*2)[:-1].tolist()
arcs = [Arc(angles_offset[i], angles[i]) for i in range(n_elements)]
arcs2 = copy.deepcopy(arcs)
triangles = [Polygon(*[
# first element
(radius*np.cos(angles_offset[i]), radius*np.sin(angles_offset[i]),0),
(0, 0, 0), # second element
# third element
(radius*np.cos(angles_offset[(i+1)%n_elements]),
radius*np.sin(angles_offset[(i+1)%n_elements]), 0)], stroke_width=0)
for i in range(n_elements)]
lines = [Line((0,0,0),
(radius*np.cos(angles_offset[i]), radius*np.sin(angles_offset[i]), 0))
for i in range(n_elements)]
for i in range(n_elements):
arcs2[i].set_fill(color_palette[i%len(color_palette)], opacity=0.5)
triangles[i].set_fill(color_palette[i%len(color_palette)], opacity=0.5)
self.play(
*map(lambda obj: ShowCreation(obj, run_time=1), arcs),
*map(lambda obj: ShowCreation(obj, run_time=1), lines),
)
self.play(
*map(lambda i: Transform(arcs[i], arcs2[i], runtime=1), range(n_elements)),
*map(lambda obj: FadeIn(obj, run_time=1), triangles),
)
self.wait()
weights = np.random.rand(n_elements)
weights /= weights.sum()
angles = weights*np.pi*2
angles_offset = [0]+np.cumsum(weights*np.pi*2)[:-1].tolist()
arcs2 = [Arc(angles_offset[i], angles[i]) for i in range(n_elements)]
lines2 = [Line((0,0,0),
(radius*np.cos(angles_offset[i]), radius*np.sin(angles_offset[i]), 0))
for i in range(n_elements)]
triangles2 = [Polygon(*[
# first element
(radius*np.cos(angles_offset[i]), radius*np.sin(angles_offset[i]),0),
(0, 0, 0), # second element
# third element
(radius*np.cos(angles_offset[(i+1)%n_elements]),
radius*np.sin(angles_offset[(i+1)%n_elements]), 0)], stroke_width=0)
for i in range(n_elements)]
for i in range(n_elements):
arcs2[i].set_fill(color_palette[i%len(color_palette)], opacity=0.5)
triangles2[i].set_fill(color_palette[i%len(color_palette)], opacity=0.5)
self.play(
*map(lambda i: Transform(lines[i], lines2[i],
runtime=1), range(n_elements)),
*map(lambda i: Transform(arcs[i], arcs2[i],
runtime=1), range(n_elements)),
*map(lambda i: Transform(triangles[i], triangles2[i],
runtime=1), range(n_elements)),
)
self.wait(2)
输出：
因此，我当前的程序有两个问题。我会很感激一点帮助。
1.由于我使用的是三角形和圆弧，因此您可以在下图中看到一个难看的间隙。
2.我对Arc,Triange和Line类进行了丑陋的转换，转换应该遵循圆周，而现在情况并非如此。您可以在下图中欣赏更多中间丑陋步骤之一。（如你所见，它不再是圆形的了）
回答
对于第一个问题，避免通过精确排列单独的形状来创建形状。事实上，完全避免将单独的形状完全对齐：图形渲染引擎在渲染这种情况时通常会遇到麻烦。不是从圆形线段和三角形中创建一个圆形扇区，而是创建一个单一形状来表示将作为单个单元绘制的整个扇区。在这种情况下，使用Sector类来表示扇区而不是单独的Arc和Polygon。
对于第二个问题，问题是默认情况下manim逐点计算中间形状。插值行为由形状的interpolate方法控制。通过对形状进行子类化，您可以覆盖该interpolate方法，而是从定义形状的更自然的高级参数计算中间形状：在这种情况下，中心、角度和半径。
这两个修复都包含在下面的示例中。
from manim import *
import numpy as np
class MySector(Sector):
""" Circular sector shape with a custom interpolation method. """
def interpolate(self, mobject1, mobject2, alpha, path_func=straight_path):
if not (isinstance(mobject1, MySector) and isinstance(mobject2, MySector)):
return super().interpolate(mobject1, mobject2, alpha, path_func=path_func)
for attr in (
'start_angle', 'angle',
'inner_radius', 'outer_radius',
):
v1 = getattr(mobject1, attr)
v2 = getattr(mobject2, attr)
setattr(self, attr, path_func(v1, v2, alpha))
self.arc_center = path_func(
mobject1.get_arc_center(),
mobject2.get_arc_center(),
alpha
)
self.interpolate_color(mobject1, mobject2, alpha)
self.clear_points()
self.generate_points()
return self
color_palette = [BLUE, GREEN, YELLOW, GREY_BROWN]
class TestPie(Scene):
def construct(self):
weights = np.array([2.0, 3.0, 4.0])
weights /= weights.sum()
angles = weights * TAU
angles_offset = np.cumsum((0, *angles[:-1]))
sectors1 = [
MySector(start_angle=ao, angle=a,
stroke_width=DEFAULT_STROKE_WIDTH,
fill_opacity=0)
for ao, a in zip(angles_offset, angles)
]
sectors2 = [
MySector(start_angle=ao, angle=a,
stroke_width=DEFAULT_STROKE_WIDTH,
fill_color=color_palette[i % len(color_palette)], fill_opacity=0.5)
for i, (ao, a) in enumerate(zip(angles_offset, angles))
]
self.play(
*(ShowCreation(a1, run_time=1) for a1 in sectors1)
)
self.play(
*(Transform(a1, a2, runtime=1) for (a1, a2) in zip(sectors1, sectors2))
)
self.wait()
weights = np.array([4.0, 3.0, 2.0])
weights /= weights.sum()
angles = weights * TAU
angles_offset = np.cumsum((0, *angles[:-1]))
sectors2 = [
MySector(start_angle=ao, angle=a,
stroke_width=DEFAULT_STROKE_WIDTH,
fill_color=color_palette[i % len(color_palette)], fill_opacity=0.5)
for i, (ao, a) in enumerate(zip(angles_offset, angles))
]
self.play(
*(Transform(a1, a2, runtime=1) for (a1, a2) in zip(sectors1, sectors2))
)
self.wait(2)
这是由此产生的动画：
以上不保留构成饼图扇区的线条的初始绘制动画。您可以覆盖该pointwise_become_partial方法以将其恢复，或者您可以简单地Line从原始代码中恢复形状。