3b1b-manim/manim_docs/modules/animation.md

# Animation Module README

## Overview
The animation module is the core of Manim's animation system. It provides classes and utilities for creating and managing animations of mobjects (mathematical objects).

## Key Components

### 1. Base Animation Class (`animation.py`)
- **Purpose**: Base class for all animations in Manim
- **Key Features**:
  - Manages animation timing and interpolation
  - Handles mobject updates during animation
  - Provides core animation functionality
- **Usage**:
  ```python
  class CustomAnimation(Animation):
      def interpolate(self, alpha):
          # Custom interpolation logic
          pass
  ```

### 2. Transform Animations (`transform.py`)
- **Purpose**: Handles transformations between mobjects
- **Key Classes**:
  - `Transform`: Base transformation class
  - `ReplacementTransform`: Replaces one mobject with another
  - `TransformFromCopy`: Creates a copy for transformation
  - `MoveToTarget`: Moves mobject to its target position
- **Usage**:
  ```python
  scene.play(Transform(circle, square))
  scene.play(ReplacementTransform(text1, text2))
  ```

### 3. Creation Animations (`creation.py`)
- **Purpose**: Animates the creation of mobjects
- **Key Classes**:
  - `ShowCreation`: Draws mobject from start to end
  - `Write`: Writes text or equations
  - `DrawBorderThenFill`: Draws border then fills
- **Usage**:
  ```python
  scene.play(ShowCreation(circle))
  scene.play(Write(text))
  ```

### 4. Fading Animations (`fading.py`)
- **Purpose**: Handles fade in/out animations
- **Key Classes**:
  - `FadeIn`: Fades in a mobject
  - `FadeOut`: Fades out a mobject
  - `FadeInFrom`: Fades in from a specific direction
- **Usage**:
  ```python
  scene.play(FadeIn(circle))
  scene.play(FadeOut(text))
  ```

### 5. Movement Animations (`movement.py`)
- **Purpose**: Handles movement and rotation animations
- **Key Classes**:
  - `MoveAlongPath`: Moves along a path
  - `Rotate`: Rotates mobject
  - `ApplyMethod`: Applies a method with animation
- **Usage**:
  ```python
  scene.play(MoveAlongPath(dot, path))
  scene.play(Rotate(circle, PI/2))
  ```

### 6. Composition Animations (`composition.py`)
- **Purpose**: Combines multiple animations
- **Key Classes**:
  - `AnimationGroup`: Plays animations simultaneously
  - `Succession`: Plays animations in sequence
  - `LaggedStart`: Starts animations with delay
- **Usage**:
  ```python
  scene.play(AnimationGroup(
      FadeIn(circle),
      Write(text),
      lag_ratio=0.5
  ))
  ```

### 7. Indication Animations (`indication.py`)
- **Purpose**: Highlights and draws attention to mobjects
- **Key Classes**:
  - `Flash`: Creates a flash effect
  - `Indicate`: Highlights a mobject
  - `ShowPassingFlash`: Shows a passing flash
- **Usage**:
  ```python
  scene.play(Flash(circle))
  scene.play(Indicate(text))
  ```

### 8. Update Animations (`update.py`)
- **Purpose**: Updates mobjects based on functions
- **Key Classes**:
  - `UpdateFromFunc`: Updates based on function
  - `UpdateFromAlphaFunc`: Updates based on alpha
- **Usage**:
  ```python
  def update_func(mob):
      mob.rotate(0.1)
  scene.play(UpdateFromFunc(circle, update_func))
  ```

## Interaction with Other Modules

1. **Mobject Module**:
   - Animations operate on mobjects
   - Uses mobject properties and methods for transformations
   - Interacts with mobject families and groups

2. **Scene Module**:
   - Scenes play and manage animations
   - Handles timing and synchronization
   - Manages animation queues and playback

3. **Camera Module**:
   - Animations can affect camera position
   - Camera movements are handled as animations
   - 3D animations interact with camera orientation

## Best Practices

1. **Animation Timing**:
   - Use appropriate `run_time` for smooth animations
   - Consider `lag_ratio` for sequential animations
   - Use `rate_func` for custom timing curves

2. **Performance**:
   - Group similar animations together
   - Use `AnimationGroup` for parallel animations
   - Consider using `LaggedStart` for complex sequences

3. **Code Organization**:
   - Create custom animations for reusable effects
   - Use composition for complex animations
   - Keep animations focused and modular

## Example Usage

```python
class ComplexAnimation(Scene):
    def construct(self):
        # Create mobjects
        circle = Circle()
        square = Square()
        text = Text("Example")

        # Basic animations
        self.play(ShowCreation(circle))
        self.wait()
        
        # Transform animation
        self.play(Transform(circle, square))
        self.wait()
        
        # Composition of animations
        self.play(AnimationGroup(
            FadeIn(text),
            Indicate(square),
            lag_ratio=0.5
        ))
        
        # Custom animation
        def update_func(mob, alpha):
            mob.rotate(alpha * TAU)
        self.play(UpdateFromAlphaFunc(square, update_func))
```