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