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61 lines
1.8 KiB
Python
61 lines
1.8 KiB
Python
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import warnings
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from manimlib.constants import *
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from manimlib.mobject.types.vectorized_mobject import VGroup
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from manimlib.mobject.types.vectorized_mobject import VMobject
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from manimlib.utils.rate_functions import smooth
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POINTLESS_VMOBJECT_WARNING = """
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Calling AnimatedBoundary on a VMobject with no points.
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"""
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class AnimatedBoundary(VGroup):
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CONFIG = {
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"colors": [BLUE_D, BLUE_B, BLUE_E, GREY_BROWN],
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"max_stroke_width": 3,
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"cycle_rate": 0.5,
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}
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def __init__(self, vmobject, **kwargs):
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super().__init__(**kwargs)
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if len(vmobject.points) == 0:
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warnings.warn(POINTLESS_VMOBJECT_WARNING)
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self.vmobject = vmobject
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self.boundary_copies = [
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VMobject(stroke_width=0, fill_opacity=0)
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for x in range(2)
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]
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self.add(*self.boundary_copies)
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self.total_time = 0
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self.add_updater(lambda m, dt: self.update(dt))
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def update(self, dt):
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# Not actual time, but something which passes at
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# an altered rate to make the implementation below
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# cleaner
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time = self.total_time * self.cycle_rate
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growing, fading = self.boundary_copies
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colors = self.colors
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msw = self.max_stroke_width
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index = int(time % len(colors))
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alpha = smooth(time % 1)
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if int(time) % 2 == 0:
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bounds = (0, alpha)
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else:
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bounds = (1 - alpha, 1)
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growing.pointwise_become_partial(self.vmobject, *bounds)
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growing.set_stroke(colors[index], width=msw)
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if time > 1:
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fading.pointwise_become_partial(self.vmobject, 0, 1)
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fading.set_stroke(
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color=colors[index - 1],
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width=(1 - alpha) * msw
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)
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self.total_time += dt
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