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Improve point_from_proportion to account for arc length

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Grant Sanderson
2021-11-16 17:28:48 -08:00
parent 82bd02d21f
commit 0e78027186
1 changed files with 26 additions and 2 deletions
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28
manimlib/mobject/types/vectorized_mobject.py
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@ -12,6 +12,7 @@ from manimlib.utils.bezier import get_smooth_quadratic_bezier_handle_points
from manimlib.utils.bezier import get_smooth_cubic_bezier_handle_points
from manimlib.utils.bezier import get_quadratic_approximation_of_cubic
from manimlib.utils.bezier import interpolate
from manimlib.utils.bezier import inverse_interpolate
from manimlib.utils.bezier import integer_interpolate
from manimlib.utils.bezier import partial_quadratic_bezier_points
from manimlib.utils.color import rgb_to_hex
@ -546,12 +547,35 @@ class VMobject(Mobject):
def get_num_curves(self):
return self.get_num_points() // self.n_points_per_curve
def point_from_proportion(self, alpha):
def quick_point_from_proportion(self, alpha):
# Assumes all curves have the same length, so is inaccurate
num_curves = self.get_num_curves()
n, residue = integer_interpolate(0, num_curves, alpha)
curve_func = self.get_nth_curve_function(n)
return curve_func(residue)
def point_from_proportion(self, alpha):
if alpha <= 0:
return self.get_start()
elif alpha >= 1:
return self.get_end()
partials = [0]
for tup in self.get_bezier_tuples():
# Approximate length with straight line from start to end
arclen = get_norm(tup[0] - tup[-1])
partials.append(partials[-1] + arclen)
full = partials[-1]
if full == 0:
return self.get_start()
# First index where the partial lenth is more alpha times the full length
i = next(
(i for i, x in enumerate(partials) if x >= full * alpha),
len(partials) # Default
)
residue = inverse_interpolate(partials[i - 1] / full, partials[i] / full, alpha)
return self.get_nth_curve_function(i - 1)(residue)
def get_anchors_and_handles(self):
"""
returns anchors1, handles, anchors2,
@ -706,7 +730,7 @@ class VMobject(Mobject):
if len(points) == 1:
return np.repeat(points, nppc * n, 0)
bezier_groups = self.get_bezier_tuples_from_points(points)
bezier_groups = list(self.get_bezier_tuples_from_points(points))
norms = np.array([
get_norm(bg[nppc - 1] - bg[0])
for bg in bezier_groups