Lightning - 3D Voxel Animation Learning Example

This guide walks you through how to generate a looping 3D voxel animation of lightning using SpatialStudio. The script creates dynamic lightning bolts that branch, flicker, and illuminate inside a cubic 3D space, then saves the animation to a .splv file.

What this script does

Creates a 3D scene of size 128×128×128
Spawns multiple lightning bolts, each with:
- Jagged, branching paths from top to bottom
- Flickering intensity and brightness variations
- Electric blue-white glow effects
- Secondary branch forks for realism
Animates them crackling and shifting for 6 seconds at 30 FPS
Outputs the file lightning.splv that you can play in your viewer

How it works (simplified)

Voxel volume Each frame is a 3D grid filled with RGBA values (SIZE × SIZE × SIZE × 4).
Lightning paths Bolts are generated using random walks with downward bias, creating natural zigzag patterns.
Branching system Main bolts spawn secondary branches at random points, creating tree-like electrical discharge.
Glow effects Each lightning segment gets surrounding voxels with dimmer colors to simulate electrical glow.
Flickering animation Brightness and visibility vary using sine waves and noise for realistic electrical behavior.
Animation loop A normalized time variable t cycles from 0 → 2π, with lightning paths shifting and flickering smoothly.
Encoding Frames are passed into splv.Encoder, which writes them into the .splv video file.

Try it yourself

Install requirements first:

pip install spatialstudio numpy tqdm

Then copy this script into lightning.py and run:

python lightning.py

Full Script

import numpy as np
from spatialstudio import splv
from tqdm import tqdm
import random

# Scene setup
SIZE, FPS, SECONDS = 128, 30, 6
FRAMES = FPS * SECONDS
CENTER_X = CENTER_Y = CENTER_Z = SIZE // 2
OUT_PATH = "../outputs/lightning.splv"

# Lightning settings
BOLT_COUNT = 3
MAX_BRANCHES = 5
GLOW_RADIUS = 2

def add_voxel(volume, x, y, z, color, alpha=255):
    if 0 <= x < SIZE and 0 <= y < SIZE and 0 <= z < SIZE:
        volume[x, y, z, :3] = color
        volume[x, y, z, 3] = alpha

def add_glow(volume, x, y, z, core_color, intensity=0.3):
    for dx in range(-GLOW_RADIUS, GLOW_RADIUS+1):
        for dy in range(-GLOW_RADIUS, GLOW_RADIUS+1):
            for dz in range(-GLOW_RADIUS, GLOW_RADIUS+1):
                dist = np.sqrt(dx*dx + dy*dy + dz*dz)
                if dist <= GLOW_RADIUS and dist > 0:
                    glow_intensity = intensity * (1 - dist/GLOW_RADIUS)
                    glow_color = tuple(int(c * glow_intensity) for c in core_color)
                    add_voxel(volume, x+dx, y+dy, z+dz, glow_color, int(255 * glow_intensity))

def generate_lightning_path(start_x, start_y, start_z, end_y, randomness=3):
    path = []
    x, y, z = start_x, start_y, start_z
    
    while y > end_y:
        path.append((x, y, z))
        
        # Move downward with random horizontal drift
        y -= random.randint(1, 3)
        x += random.randint(-randomness, randomness)
        z += random.randint(-randomness, randomness)
        
        # Keep within bounds
        x = max(5, min(SIZE-5, x))
        z = max(5, min(SIZE-5, z))
    
    return path

def generate_branches(main_path, branch_count=2):
    branches = []
    if len(main_path) < 10:
        return branches
        
    for _ in range(branch_count):
        # Pick random point along main path (not too early)
        branch_start_idx = random.randint(len(main_path)//4, len(main_path)-5)
        start_point = main_path[branch_start_idx]
        
        # Generate shorter branch
        branch_length = random.randint(5, 15)
        branch = []
        x, y, z = start_point
        
        for _ in range(branch_length):
            branch.append((x, y, z))
            y -= random.randint(0, 2)
            x += random.randint(-2, 2)
            z += random.randint(-2, 2)
            
            # Keep within bounds
            x = max(0, min(SIZE-1, x))
            y = max(0, min(SIZE-1, y))
            z = max(0, min(SIZE-1, z))
            
            if y <= 5:  # Don't go too low
                break
                
        branches.append(branch)
    
    return branches

def draw_lightning_segment(volume, path, color, brightness=1.0, t=0):
    for i, (x, y, z) in enumerate(path):
        # Add some flickering
        flicker = 0.7 + 0.3 * np.sin(t * 10 + i * 0.5)
        segment_brightness = brightness * flicker
        
        # Core lightning color
        core_color = tuple(int(c * segment_brightness) for c in color)
        add_voxel(volume, x, y, z, core_color)
        
        # Add glow around each segment
        add_glow(volume, x, y, z, color, 0.4 * segment_brightness)

def generate_lightning_bolts(volume, t):
    # Lightning colors (blue-white electrical)
    colors = [
        (200, 220, 255),  # Bright blue-white
        (150, 180, 255),  # Light blue
        (255, 255, 255),  # Pure white
    ]
    
    for i in range(BOLT_COUNT):
        # Vary starting positions and timing
        start_x = CENTER_X + int(20 * np.sin(i * 2.1 + t * 0.5))
        start_z = CENTER_Z + int(20 * np.cos(i * 1.7 + t * 0.3))
        
        # Generate main lightning path
        main_path = generate_lightning_path(
            start_x, SIZE - 10, start_z, 10, 
            randomness=int(3 + 2 * np.sin(t * 2 + i))
        )
        
        # Create some flickering - sometimes bolts are invisible
        visibility = np.sin(t * 15 + i * 3.7) * 0.5 + 0.5
        if visibility < 0.3:  # Bolt flickers out
            continue
            
        brightness = 0.6 + 0.4 * visibility
        color = colors[i % len(colors)]
        
        # Draw main bolt
        draw_lightning_segment(volume, main_path, color, brightness, t)
        
        # Generate and draw branches
        branches = generate_branches(main_path, random.randint(1, MAX_BRANCHES))
        for branch in branches:
            branch_brightness = brightness * 0.6  # Branches are dimmer
            draw_lightning_segment(volume, branch, color, branch_brightness, t)

def add_atmospheric_effects(volume, t):
    # Add some random electrical particles/sparks
    spark_count = int(10 + 5 * np.sin(t * 3))
    
    for _ in range(spark_count):
        x = random.randint(10, SIZE-10)
        y = random.randint(10, SIZE-10)
        z = random.randint(10, SIZE-10)
        
        # Small bright sparks
        spark_brightness = random.uniform(0.3, 0.8)
        spark_color = (
            int(255 * spark_brightness),
            int(255 * spark_brightness),
            255
        )
        add_voxel(volume, x, y, z, spark_color, int(255 * spark_brightness))

def generate_scene(volume, t):
    generate_lightning_bolts(volume, t)
    add_atmospheric_effects(volume, t)

# Initialize encoder
enc = splv.Encoder(SIZE, SIZE, SIZE, framerate=FPS, outputPath=OUT_PATH, motionVectors="off")

# Generate frames
for frame in tqdm(range(FRAMES), desc="Generating lightning"):
    volume = np.zeros((SIZE, SIZE, SIZE, 4), dtype=np.uint8)
    t = (frame / FRAMES) * 2*np.pi
    
    # Reset random seed occasionally for variation
    if frame % 10 == 0:
        random.seed(frame // 10)
    
    generate_scene(volume, t)
    enc.encode(splv.Frame(volume, lrAxis="x", udAxis="y", fbAxis="z"))

enc.finish()
print(f"Created {OUT_PATH}")

Next steps

Change BOLT_COUNT to create more or fewer lightning bolts.
Adjust MAX_BRANCHES for more complex branching patterns.
Modify the colors array to create different types of electrical effects (red plasma, green energy, etc.).
Increase GLOW_RADIUS for more dramatic lighting effects.
Add thunder clouds by creating gray voxel clusters at the top of the scene.

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Lightning - 3D Voxel Animation Learning Example

What this script does

How it works (simplified)