Sync all skills and memories 2026-04-14 07:27

skills/creative/manim-video/references/camera-and-3d.md

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+# Camera and 3D Reference
+
+## MovingCameraScene (2D Camera Control)
+
+```python
+class ZoomExample(MovingCameraScene):
+    def construct(self):
+        circle = Circle(radius=2, color=BLUE)
+        self.play(Create(circle))
+        # Zoom in
+        self.play(self.camera.frame.animate.set(width=4).move_to(circle.get_top()), run_time=2)
+        self.wait(2)
+        # Zoom back out
+        self.play(self.camera.frame.animate.set(width=14.222).move_to(ORIGIN), run_time=2)
+```
+
+### Camera Operations
+
+```python
+self.camera.frame.animate.set(width=6)     # zoom in
+self.camera.frame.animate.set(width=20)    # zoom out
+self.camera.frame.animate.move_to(target)  # pan
+self.camera.frame.save_state()             # save
+self.play(Restore(self.camera.frame))      # restore
+```
+
+## ThreeDScene
+
+```python
+class ThreeDExample(ThreeDScene):
+    def construct(self):
+        self.set_camera_orientation(phi=60*DEGREES, theta=-45*DEGREES)
+        axes = ThreeDAxes()
+        surface = Surface(
+            lambda u, v: axes.c2p(u, v, np.sin(u) * np.cos(v)),
+            u_range=[-PI, PI], v_range=[-PI, PI], resolution=(30, 30)
+        )
+        surface.set_color_by_gradient(BLUE, GREEN, YELLOW)
+        self.play(Create(axes), Create(surface))
+        self.begin_ambient_camera_rotation(rate=0.2)
+        self.wait(5)
+        self.stop_ambient_camera_rotation()
+```
+
+### Camera Control in 3D
+
+```python
+self.set_camera_orientation(phi=70*DEGREES, theta=-45*DEGREES)
+self.move_camera(phi=45*DEGREES, theta=30*DEGREES, run_time=2)
+self.begin_ambient_camera_rotation(rate=0.2)
+```
+
+### 3D Mobjects
+
+```python
+sphere = Sphere(radius=1).set_color(BLUE).set_opacity(0.7)
+cube = Cube(side_length=2, fill_color=GREEN, fill_opacity=0.5)
+arrow = Arrow3D(start=ORIGIN, end=[2, 1, 1], color=RED)
+# 2D text facing camera:
+label = Text("Label", font_size=30)
+self.add_fixed_in_frame_mobjects(label)
+```
+
+### Parametric Curves
+
+```python
+helix = ParametricFunction(
+    lambda t: [np.cos(t), np.sin(t), t / (2*PI)],
+    t_range=[0, 4*PI], color=YELLOW
+)
+```
+
+## When to Use 3D
+- Surfaces, vector fields, spatial geometry, 3D transforms
+## When NOT to Use 3D
+- 2D concepts, text-heavy scenes, flat data (bar charts, time series)
+
+## ZoomedScene — Inset Zoom
+
+Show a magnified inset of a detail while keeping the full view visible:
+
+```python
+class ZoomExample(ZoomedScene):
+    def __init__(self, **kwargs):
+        super().__init__(
+            zoom_factor=0.3,           # how much of the scene the zoom box covers
+            zoomed_display_height=3,   # size of the inset
+            zoomed_display_width=3,
+            zoomed_camera_frame_starting_position=ORIGIN,
+            **kwargs
+        )
+
+    def construct(self):
+        self.camera.background_color = BG
+        # ... create your scene content ...
+
+        # Activate the zoom
+        self.activate_zooming()
+
+        # Move the zoom frame to a point of interest
+        self.play(self.zoomed_camera.frame.animate.move_to(detail_point))
+        self.wait(2)
+
+        # Deactivate
+        self.play(self.get_zoomed_display_pop_out_animation(), rate_func=lambda t: smooth(1-t))
+```
+
+Use cases: zooming into a specific term in an equation, showing fine detail in a diagram, magnifying a region of a plot.
+
+## LinearTransformationScene — Linear Algebra
+
+Pre-built scene with basis vectors and grid for visualizing matrix transformations:
+
+```python
+class LinearTransformExample(LinearTransformationScene):
+    def __init__(self, **kwargs):
+        super().__init__(
+            show_coordinates=True,
+            show_basis_vectors=True,
+            **kwargs
+        )
+
+    def construct(self):
+        matrix = [[2, 1], [1, 1]]
+
+        # Add a vector before applying the transform
+        vector = self.get_vector([1, 2], color=YELLOW)
+        self.add_vector(vector)
+
+        # Apply the transformation — grid, basis vectors, and your vector all transform
+        self.apply_matrix(matrix)
+        self.wait(2)
+```
+
+This produces the signature 3Blue1Brown "Essence of Linear Algebra" look — grid lines deforming, basis vectors stretching, determinant visualized through area change.