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Improved Arc, and added Sector

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This commit is contained in:
Grant Sanderson 2018-01-17 15:12:39 -08:00
parent de478a515a
commit cd2257ad65
1 changed files with 55 additions and 10 deletions
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65
topics/geometry.py
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@ -15,25 +15,35 @@ class Arc(VMobject):
VMobject.__init__(self, **kwargs)
def generate_points(self):
self.set_anchor_points(
self.get_unscaled_anchor_points(),
mode = "smooth"
)
self.scale(self.radius)
def get_unscaled_anchor_points(self):
return [
anchors = np.array([
np.cos(a)*RIGHT+np.sin(a)*UP
for a in np.linspace(
self.start_angle,
self.start_angle + self.angle,
self.num_anchors
)
]
])
#Figure out which control points will give the
#Appropriate tangent lines to the circle
d_theta = self.angle/(self.num_anchors-1.0)
tangent_vectors = np.zeros(anchors.shape)
tangent_vectors[:,1] = anchors[:,0]
tangent_vectors[:,0] = -anchors[:,1]
handles1 = anchors[:-1] + (d_theta/3)*tangent_vectors[:-1]
handles2 = anchors[1:] - (d_theta/3)*tangent_vectors[1:]
self.set_anchors_and_handles(
anchors, handles1, handles2
)
self.scale(self.radius, about_point = ORIGIN)
def add_tip(self, tip_length = 0.25):
#TODO, do this a better way
arrow = Arrow(*self.points[-2:], tip_length = tip_length)
p1, p2 = self.points[-2:]
arrow = Arrow(
p1, 2*p2 - p1,
tip_length = tip_length,
max_tip_length_to_length_ratio = 2.0
)
self.add(arrow.split()[-1])
self.highlight(self.get_color())
return self
@ -66,6 +76,41 @@ class Dot(Circle):
self.shift(point)
self.init_colors()
class Sector(VMobject):
CONFIG = {
"inner_radius" : 1,
"outer_radius" : 2,
"angle" : TAU/4,
"start_angle" : 0,
"fill_opacity" : 1,
"stroke_width" : 0,
"color" : WHITE,
"mark_paths_closed" : True,
}
def generate_points(self):
arc1 = Arc(
angle = self.angle,
start_angle = self.start_angle,
radius = self.inner_radius,
)
arc2 = Arc(
angle = -1*self.angle,
start_angle = self.start_angle+self.angle,
radius = self.outer_radius,
)
a1_to_a2_points = np.array([
interpolate(arc1.points[-1], arc2.points[0], alpha)
for alpha in np.linspace(0, 1, 4)
])
a2_to_a1_points = np.array([
interpolate(arc2.points[-1], arc1.points[0], alpha)
for alpha in np.linspace(0, 1, 4)
])
self.points = np.array(arc1.points)
self.add_control_points(a1_to_a2_points[1:])
self.add_control_points(arc2.points[1:])
self.add_control_points(a2_to_a1_points[1:])
class Line(VMobject):
CONFIG = {
"buff" : 0,