1 files changed, 55 insertions, 0 deletions
diff --git a/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Curl and Div/DivCurl_file8_curl-paddle.py b/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Curl and Div/DivCurl_file8_curl-paddle.py
new file mode 100644
index 0000000..7a11992
--- /dev/null
+++ b/FSF-2020/calculus-of-several-variables/div-curl-grad-and-all-that/Curl and Div/DivCurl_file8_curl-paddle.py
@@ -0,0 +1,55 @@
+from manimlib.imports import *
+
+def field_func(coordinate):
+	x,y = coordinate[:2]
+	return np.array([
+					-y, 
+					x,
+					0
+				])
+
+class Paddlewheel(ThreeDScene):
+	def construct(self):
+		axes = ThreeDAxes()
+		#self.add(axes)
+		text = TextMobject("Insert the paddle into the flow of water").shift(3*DOWN).add_background_rectangle()
+		text_a = TextMobject("The rotation of the wheel is proportional to the component of curl in the direction of the axle").shift(3*DOWN).scale(0.7)
+
+		vec_field = VectorField(field_func, x_min =-4, x_max = 4, y_min =-4, y_max =4)
+
+		self.set_camera_orientation(phi=0*DEGREES,theta=0*DEGREES,distance=40)
+		lines_a = StreamLines(
+			field_func,
+			virtual_time=3,
+			min_magnitude=0,
+			max_magnitude=3,
+		).set_color_by_gradient([WHITE, BLUE_E])
+		flow = AnimatedStreamLines(
+			lines_a,
+			line_anim_class=ShowPassingFlashWithThinningStrokeWidth
+		)
+
+		paddle = VGroup(Line(np.array([3, 0, 0]), np.array([-3, 0, 0])),
+						Line(np.array([0, 3, 0]), np.array([0, -3, 0]))).set_stroke(width = 8).set_color(YELLOW_E)
+		cylinder = ParametricSurface(
+		lambda u, v: np.array([
+		0.1*np.cos(u),
+		0.1*np.sin(u),
+		v,
+		]), 
+		u_min = 0, u_max = 2*np.pi, v_min = -0.2, v_max = 3.5, checkerboard_colors = [YELLOW_E, YELLOW_E]).fade(0.5)
+		plane = ParametricSurface(lambda u, v: np.array([u, v, 0]), checkerboard_colors = [WHITE, WHITE]).fade(0.9)
+
+		self.add(paddle, cylinder, flow)
+		self.add_fixed_in_frame_mobjects(text)
+		self.play(Rotating(paddle))
+		self.wait()
+		self.play(FadeIn(vec_field))
+		self.remove(flow, text)
+		self.bring_to_front(cylinder)
+		#self.play(Rotating(paddle))
+		self.wait()
+		self.add_fixed_in_frame_mobjects(text_a)
+		#self.play(ReplacementTransform(text, text_a))
+		self.move_camera(phi=60*DEGREES,theta=30*DEGREES)
+		self.wait()