Photon through lens

brachistochrone/curves.py

@@ -323,39 +323,6 @@ class RollingRandolph(PathSlidingScene):
 
 
 
-class OceanScene(Scene):
-    def construct(self):
-        self.rolling_waves()
-
-    def rolling_waves(self):
-        if not hasattr(self, "ocean"):
-            self.setup_ocean()
-        for state in self.ocean_states:
-            self.play(Transform(self.ocean, state))
-
-
-    def setup_ocean(self):
-        def func(points):
-            result = np.zeros(points.shape)
-            result[:,1] = 0.25 * np.sin(points[:,0]) * np.sin(points[:,1])
-            return result
-
-        self.ocean_states = []
-        for unit in -1, 1:
-            ocean = FilledRectangle(
-                color = BLUE_D, 
-                density = 25
-            )
-            nudges = unit*func(ocean.points)
-            ocean.points += nudges
-            alphas = nudges[:,1]
-            alphas -= np.min(alphas)
-            whites = np.ones(ocean.rgbs.shape)
-            thick_alphas = alphas.repeat(3).reshape((len(alphas), 3))
-            ocean.rgbs = interpolate(ocean.rgbs, whites, thick_alphas)
-            self.ocean_states.append(ocean)
-        self.ocean = self.ocean_states[1].copy()
-
 
 
 

brachistochrone/light.py

@@ -27,6 +27,26 @@ from topics.number_line import NumberPlane
 from region import Region, region_from_polygon_vertices
 from scene import Scene
 
+from brachistochrone.curves import Cycloid
+
+class Lens(Arc):
+    DEFAULT_CONFIG = {
+        "radius" : 2,
+        "angle" : np.pi/2,
+        "color" : BLUE_B,
+    }
+    def __init__(self, **kwargs):
+        digest_config(self, kwargs)
+        Arc.__init__(self, self.angle, **kwargs)
+
+    def generate_points(self):
+        Arc.generate_points(self)
+        self.rotate(-np.pi/4)
+        self.shift(-self.get_left())
+        self.add_points(self.copy().rotate(np.pi).points)
+
+
+
 class PhotonScene(Scene):
     def wavify(self, mobject):
         tangent_vectors = mobject.points[1:]-mobject.points[:-1]
@@ -46,14 +66,11 @@ class PhotonScene(Scene):
         result.points[1:] += nudges
         return result
 
-    def photon_along_path(self, path, color = YELLOW, run_time = 1):
+
+    def photon_run_along_path(self, path, color = YELLOW, **kwargs):
         photon = self.wavify(path)
         photon.highlight(color)
-        self.play(ShowPassingFlash(
+        return ShowPassingFlash(photon, **kwargs)
-            photon, 
-            run_time = run_time,
-            rate_func = None
-        ))
 
 
 class SimplePhoton(PhotonScene):
@@ -61,5 +78,60 @@ class SimplePhoton(PhotonScene):
         text = TextMobject("Light")
         text.to_edge(UP)
         self.play(ShimmerIn(text))
-        self.photon_along_path(Cycloid())
+        self.play(self.photon_run_along_path(
-        self.dither()
+            Cycloid(), rate_func = None
+        ))
+        self.dither()
+
+
+class PhotonThroughLens(PhotonScene):
+    def construct(self):
+        lens = Lens()
+        num_paths = 5
+        interval_values = np.arange(num_paths)/(num_paths-1.)
+        first_contact = [
+            lens.point_from_interval(0.4*v+0.55)
+            for v in reversed(interval_values)
+        ]
+        second_contact = [
+            lens.point_from_interval(0.3*v + 0.1)
+            for v in interval_values
+        ]
+        focal_point = 2*RIGHT
+        paths = [
+            Mobject(
+                Line(SPACE_WIDTH*LEFT + fc[1]*UP, fc),
+                Line(fc, sc),
+                Line(sc, focal_point),
+                Line(focal_point, 6*focal_point-5*sc)
+            ).ingest_sub_mobjects()
+            for fc, sc in zip(first_contact, second_contact)
+        ]
+        colors = Color(YELLOW).range_to(WHITE, len(paths))
+        for path, color in zip(paths, colors):
+            path.highlight(color)
+        photon_runs = [
+            self.photon_run_along_path(path)
+            for path in paths
+        ]
+        self.add(lens)
+        for photon_run, path in zip(photon_runs, paths):
+            self.play(
+                photon_run,
+                ShowCreation(
+                    path,
+                    rate_func = lambda t : 0.9*smooth(t)
+                )
+            )
+        self.dither()
+
+
+
+
+
+
+
+
+
+
+

constants.py

@@ -19,8 +19,8 @@ MEDIUM_QUALITY_DISPLAY_CONFIG = {
 }
 
 LOW_QUALITY_DISPLAY_CONFIG = {
-    "height"         : 480,
+    "height"         : 600,#480,
-    "width"          : 840,
+    "width"          : 1000,#840,
     "frame_duration" : 0.04,
 }
 

mobject/mobject.py

@@ -460,6 +460,9 @@ class Mobject(object):
     def get_height(self):
         return self.length_over_dim(1)
 
+    def point_from_interval(self, alpha):
+        index = alpha*(self.get_num_points()-1)
+        return self.points[index]
 
     def get_color(self):
         color = Color()