1 files changed, 63 insertions, 0 deletions
diff --git a/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Conservative fields/Conservative_file5_closed-loop.py b/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Conservative fields/Conservative_file5_closed-loop.py
new file mode 100644
index 0000000..9211f0d
--- /dev/null
+++ b/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Conservative fields/Conservative_file5_closed-loop.py
@@ -0,0 +1,63 @@
+from manimlib.imports import *
+import numpy as np
+
+def div(coordinate):
+	x,y = coordinate[:2]
+	return np.array([
+			x,
+			y,
+			0
+	])
+
+
+class Loop(Scene):
+	def get_pending(self,path,proportion,dx=0.01):
+		if proportion < 1:
+			coord_i = path.point_from_proportion(proportion)
+			coord_f = path.point_from_proportion(proportion+dx)
+		else:
+			coord_i = path.point_from_proportion(proportion-dx)
+			coord_f = path.point_from_proportion(proportion)
+		line = Line(coord_i,coord_f)
+		angle = line.get_angle()
+		return angle
+	def construct(self):
+
+
+
+		boundary = VMobject(stroke_color = "#F4EDED")
+		boundary.set_points_smoothly([np.array([-2, 1.8,0]),np.array([-1.6, 0.5,0]),np.array([-3.2, -1.2,0]),np.array([2.6, -1.5,0]),np.array([1, 0,0]),np.array([3.5,2.3, 0]), np.array([-2,1.8, 0])])
+		#c = TexMobject(r"C").next_to(surf,RIGHT+UP).set_color("#F4EDED")
+
+
+		text = TexMobject(r"\oint \vec F \cdot \vec dr", r" = 0").shift(3*DOWN).set_stroke(width = 1.5)
+		vec_field = VectorField(div)
+
+		start_angle = self.get_pending(boundary, 0)
+
+		pointer = Triangle(fill_opacity = 1).set_height(0.25).set_color(WHITE)
+		pointer.set_fill(WHITE)
+		pointer.move_to(boundary.get_start())
+		pointer.rotate(- PI / 2)
+		pointer.save_state()
+		pointer.rotate(start_angle, about_point=pointer.get_center())
+		
+
+		self.play(ShowCreation(boundary), ShowCreation(vec_field))
+		self.wait()
+		self.play(Write(text[0]))
+		def update_rotate_move(mob,alpha):
+			pointer.restore()
+
+			angle = self.get_pending(boundary,alpha)
+
+			pointer.move_to(boundary.point_from_proportion(alpha))
+			pointer.rotate(angle, about_point=pointer.get_center())
+		self.play(
+			#self.camera_frame.scale,.25,
+			UpdateFromAlphaFunc(pointer,update_rotate_move),
+			run_time=3,
+			)
+		self.play(ShowCreation(text[1]))
+		self.play(Indicate(text))
+		self.wait()