plot_animation.py

#!/usr/bin/env python3
"""
Generate an animation GIF of a single Schrödinger equation sample time evolution.

Animates quantum wave packet dynamics including:
- Real and imaginary parts of wavefunction
- Probability density |ψ|²
- Wave packet motion in harmonic potential
"""

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from dataset import SchrodingerDataset


def create_schrodinger_animation(sample, save_path="sample_animation.gif", fps=15):
    """Create an animation GIF from a Schrödinger sample"""
    # Extract data
    x = sample['spatial_coordinates']
    t = sample['time_coordinates']
    psi_r = sample['psi_r_trajectory']
    psi_i = sample['psi_i_trajectory']
    prob = sample['probability_density']
    V = sample['potential']
    energy = sample['total_energy']
    
    # Set up the figure with subplots
    fig, (ax1, ax2, ax3) = plt.subplots(3, 1, figsize=(12, 10))
    fig.suptitle(f'Quantum Harmonic Oscillator Evolution\n' + 
                 f'ℏ={sample["hbar"]}, m={sample["mass"]}, ω={sample["omega"]}', 
                 fontsize=14, fontweight='bold')
    
    # Colors for consistency
    color_real = '#1f77b4'
    color_imag = '#ff7f0e'
    color_prob = '#2ca02c'
    color_potential = '#d62728'
    
    # Subplot 1: Wavefunction components
    ax1.set_xlim(x[0], x[-1])
    psi_max = max(np.max(np.abs(psi_r)), np.max(np.abs(psi_i))) * 1.1
    ax1.set_ylim(-psi_max, psi_max)
    ax1.set_ylabel('ψ(x,t)')
    ax1.set_title('Wavefunction Components')
    ax1.grid(True, alpha=0.3)
    
    # Plot potential well (scaled for background)
    V_scaled = V / np.max(V) * psi_max * 0.2
    ax1.fill_between(x, -psi_max, V_scaled - psi_max, alpha=0.1, color=color_potential)
    ax1.plot(x, V_scaled - psi_max, '--', alpha=0.5, color=color_potential, linewidth=1, label='V(x)')
    
    real_line, = ax1.plot([], [], color=color_real, linewidth=2, label='ψᵣ(x,t)')
    imag_line, = ax1.plot([], [], color=color_imag, linewidth=2, label='ψᵢ(x,t)')
    ax1.legend(loc='upper right')
    
    # Subplot 2: Probability density
    ax2.set_xlim(x[0], x[-1])
    prob_max = np.max(prob) * 1.1
    ax2.set_ylim(0, prob_max)
    ax2.set_ylabel('|ψ(x,t)|²')
    ax2.set_title('Probability Density')
    ax2.grid(True, alpha=0.3)
    
    # Plot potential well (scaled for background)
    V_scaled_prob = V / np.max(V) * prob_max * 0.3
    ax2.fill_between(x, V_scaled_prob, alpha=0.2, color=color_potential)
    
    prob_line, = ax2.plot([], [], color=color_prob, linewidth=2, label='|ψ|²')
    ax2.legend(loc='upper right')
    
    # Subplot 3: Energy over time
    ax3.set_xlim(t[0], t[-1])
    E_mean = np.mean(energy)
    E_range = np.max(energy) - np.min(energy)
    if E_range > 0:
        ax3.set_ylim(np.min(energy) - 0.1*E_range, np.max(energy) + 0.1*E_range)
    else:
        ax3.set_ylim(E_mean - 0.1*abs(E_mean), E_mean + 0.1*abs(E_mean))
        
    ax3.set_xlabel('Time t')
    ax3.set_ylabel('Total Energy')
    ax3.set_title('Energy Conservation')
    ax3.grid(True, alpha=0.3)
    
    # Plot full energy trace as background
    ax3.plot(t, energy, 'k-', alpha=0.3, linewidth=1)
    ax3.axhline(E_mean, color='red', linestyle='--', alpha=0.7, linewidth=1)
    
    # Current energy point
    energy_point, = ax3.plot([], [], 'o', color='darkgreen', markersize=8)
    energy_line, = ax3.plot([], [], color='darkgreen', linewidth=2)
    
    # Time text
    time_text = fig.text(0.02, 0.02, '', fontsize=12, fontweight='bold',
                        bbox=dict(boxstyle="round,pad=0.3", facecolor='yellow', alpha=0.7))
    
    # Store fill object
    prob_fill = None
    
    def animate(frame):
        """Animation function"""
        nonlocal prob_fill
        
        # Update wavefunction components
        real_line.set_data(x, psi_r[frame])
        imag_line.set_data(x, psi_i[frame])
        
        # Update probability density
        prob_line.set_data(x, prob[frame])
        
        # Remove old fill and create new one
        if prob_fill is not None:
            prob_fill.remove()
        prob_fill = ax2.fill_between(x, prob[frame], alpha=0.3, color=color_prob)
        
        # Update energy plot
        current_t = t[:frame+1]
        current_e = energy[:frame+1]
        energy_line.set_data(current_t, current_e)
        energy_point.set_data([t[frame]], [energy[frame]])
        
        # Update time display
        time_text.set_text(f'Time: {t[frame]:.3f} / {t[-1]:.3f}')
        
        return real_line, imag_line, prob_line, energy_line, energy_point, time_text
    
    # Create animation with more frames for smoother motion
    print(f"Creating animation with {len(t)} frames...")
    anim = animation.FuncAnimation(
        fig, animate, frames=len(t),
        interval=1000/fps, blit=False, repeat=True  # blit=False due to fill_between
    )
    
    # Save as GIF
    print(f"Saving animation to {save_path}...")
    anim.save(save_path, writer='pillow', fps=fps)
    plt.close()
    
    print(f"Animation saved to {save_path}")


def create_simple_animation(sample, save_path="simple_animation.gif", fps=15):
    """Create a simpler single-panel animation focusing on probability density"""
    # Extract data
    x = sample['spatial_coordinates']
    t = sample['time_coordinates']
    prob = sample['probability_density']
    V = sample['potential']
    
    # Set up single plot
    fig, ax = plt.subplots(figsize=(10, 6))
    ax.set_xlim(x[0], x[-1])
    prob_max = np.max(prob) * 1.1
    ax.set_ylim(0, prob_max)
    ax.set_xlabel('Position x')
    ax.set_ylabel('Probability Density |ψ|²')
    ax.set_title(f'Quantum Wave Packet in Harmonic Oscillator\n' +
                 f'ℏ={sample["hbar"]}, m={sample["mass"]}, ω={sample["omega"]}')
    ax.grid(True, alpha=0.3)
    
    # Plot potential well (scaled)
    V_scaled = V / np.max(V) * prob_max * 0.3
    ax.fill_between(x, V_scaled, alpha=0.2, color='red', label='V(x) (scaled)')
    ax.plot(x, V_scaled, 'r--', alpha=0.7, linewidth=1)
    
    # Initialize probability line
    prob_line, = ax.plot([], [], 'b-', linewidth=3, label='|ψ(x,t)|²')
    
    # Time text
    time_text = ax.text(0.02, 0.95, '', transform=ax.transAxes, fontsize=12,
                       bbox=dict(boxstyle="round", facecolor='white', alpha=0.8))
    
    ax.legend()
    
    # Store fill object
    prob_fill = None
    
    def animate(frame):
        """Simple animation function"""
        nonlocal prob_fill
        
        # Update probability line
        prob_line.set_data(x, prob[frame])
        
        # Remove previous fill if it exists
        if prob_fill is not None:
            prob_fill.remove()
        
        # Create new fill
        prob_fill = ax.fill_between(x, prob[frame], alpha=0.4, color='blue')
        
        # Update time text
        time_text.set_text(f'Time: {t[frame]:.3f}')
        return prob_line, time_text
    
    # Create animation
    anim = animation.FuncAnimation(
        fig, animate, frames=len(t),
        interval=1000/fps, blit=False, repeat=True
    )
    
    # Save as GIF
    anim.save(save_path, writer='pillow', fps=fps)
    plt.close()
    
    print(f"Simple animation saved to {save_path}")


if __name__ == "__main__":
    # Set random seed for reproducibility
    np.random.seed(42)
    
    # Create dataset
    dataset = SchrodingerDataset(
        Lx=20.0,
        Nx=128,  # Lower resolution for faster animation generation
        stop_sim_time=3.0,
        timestep=2e-3  # Slightly larger timestep for fewer frames
    )
    
    # Generate a single sample
    sample = next(iter(dataset))
    
    print("Creating animations...")
    print(f"Time steps: {len(sample['time_coordinates'])}")
    print(f"Spatial points: {len(sample['spatial_coordinates'])}")
    
    # Create both animations
    create_simple_animation(sample, "simple_animation.gif", fps=12)
    create_schrodinger_animation(sample, "sample_animation.gif", fps=10)