Earth Orbit Animation - 3D Voxel Learning Example

This guide walks you through how to generate a looping 3D voxel animation of Earth orbiting the Sun using SpatialStudio. The script creates a realistic solar system scene with Earth rotating on its axis while orbiting around a glowing Sun, then saves the animation to a .splv file.

What this script does

Creates a 3D scene of size 128×128×128
Renders a glowing Sun at the center with:
- Dynamic solar flares
- Pulsing brightness effects
- Radiating heat particles
Animates Earth with realistic motion:
- Orbital revolution around the Sun
- Axial rotation (day/night cycle)
- Blue oceans and green/brown continents
- Atmospheric glow effect
Runs for 12 seconds at 30 FPS for a complete orbit
Outputs the file earth_orbit.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).
Sun rendering The Sun is drawn as a large glowing sphere with animated surface details and particle effects.
Earth generation Earth features procedurally generated continents using noise functions and rotates to show different faces.
Orbital mechanics Earth follows an elliptical path around the Sun while spinning on its own axis at a realistic speed ratio.
Lighting effects The Sun-facing side of Earth is brighter, with atmospheric scattering creating a blue rim effect.
Animation loop A normalized time variable t cycles from 0 → 2π, ensuring one complete orbit loops 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 earth_orbit.py and run:

python earth_orbit.py

Full Script

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

# Scene setup
SIZE, FPS, SECONDS = 128, 30, 12
FRAMES = FPS * SECONDS
CENTER_X = CENTER_Y = CENTER_Z = SIZE // 2
OUT_PATH = "../outputs/earth_orbit.splv"

# Celestial body settings
SUN_RADIUS = 12
EARTH_RADIUS = 4
ORBIT_RADIUS = 35
EARTH_ROTATION_SPEED = 8.0  # Earth spins faster than it orbits

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

def noise_3d(x, y, z, scale=0.1):
    """Simple 3D noise function for terrain generation"""
    return np.sin(x*scale) * np.cos(y*scale*1.3) * np.sin(z*scale*0.7)

def generate_sun(volume, cx, cy, cz, t):
    """Generate animated sun with solar flares"""
    base_color = (255, 200, 50)
    
    for dx in range(-SUN_RADIUS-3, SUN_RADIUS+4):
        for dy in range(-SUN_RADIUS-3, SUN_RADIUS+4):
            for dz in range(-SUN_RADIUS-3, SUN_RADIUS+4):
                dist = np.sqrt(dx*dx + dy*dy + dz*dz)
                
                # Sun core
                if dist <= SUN_RADIUS:
                    flare = np.sin(dx*0.2 + dy*0.3 + dz*0.1 + t*2.0) * 0.3
                    pulse = 1.0 + np.sin(t*3.0) * 0.2
                    intensity = (1.0 + flare) * pulse
                    
                    color = tuple(min(255, max(0, int(c * intensity))) for c in base_color)
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, color)
                
                # Solar corona
                elif dist <= SUN_RADIUS + 3:
                    corona_intensity = max(0, 1.0 - (dist - SUN_RADIUS) / 3.0)
                    corona_flicker = np.sin(t*4.0 + dist*0.5) * 0.5 + 0.5
                    final_intensity = corona_intensity * corona_flicker * 0.7
                    
                    if final_intensity > 0.3:
                        corona_color = (int(255*final_intensity), int(150*final_intensity), int(20*final_intensity))
                        add_voxel(volume, cx+dx, cy+dy, cz+dz, corona_color)

def generate_earth(volume, cx, cy, cz, rotation_t, t):
    """Generate Earth with continents, oceans, and atmosphere"""
    
    for dx in range(-EARTH_RADIUS-2, EARTH_RADIUS+3):
        for dy in range(-EARTH_RADIUS-2, EARTH_RADIUS+3):
            for dz in range(-EARTH_RADIUS-2, EARTH_RADIUS+3):
                dist = np.sqrt(dx*dx + dy*dy + dz*dz)
                
                if dist <= EARTH_RADIUS:
                    # Rotate the sampling point
                    rot_x = dx * np.cos(rotation_t) - dz * np.sin(rotation_t)
                    rot_z = dx * np.sin(rotation_t) + dz * np.cos(rotation_t)
                    
                    # Generate terrain
                    terrain = noise_3d(rot_x, dy, rot_z, 0.3)
                    
                    # Determine surface type
                    if terrain > 0.1:  # Land
                        if dy > EARTH_RADIUS * 0.3:  # Mountains/arctic
                            color = (139, 90, 43) if terrain > 0.3 else (34, 139, 34)
                        else:  # Forests/plains
                            color = (34, 139, 34) if terrain > 0.25 else (160, 82, 45)
                    else:  # Ocean
                        depth = abs(terrain)
                        blue_intensity = int(255 - depth * 100)
                        color = (0, 50, max(100, blue_intensity))
                    
                    # Apply lighting based on sun direction
                    sun_dir = np.array([-cx + CENTER_X, -cy + CENTER_Y, -cz + CENTER_Z])
                    if np.linalg.norm(sun_dir) > 0:
                        sun_dir = sun_dir / np.linalg.norm(sun_dir)
                        normal = np.array([dx, dy, dz]) / dist if dist > 0 else np.array([0, 1, 0])
                        lighting = max(0.3, np.dot(normal, sun_dir) * 0.7 + 0.3)
                        color = tuple(int(c * lighting) for c in color)
                    
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, color)
                
                # Atmosphere
                elif dist <= EARTH_RADIUS + 2:
                    atmo_intensity = max(0, 1.0 - (dist - EARTH_RADIUS) / 2.0)
                    if atmo_intensity > 0.4:
                        atmo_color = (int(100*atmo_intensity), int(150*atmo_intensity), int(255*atmo_intensity))
                        add_voxel(volume, cx+dx, cy+dy, cz+dz, atmo_color)

def generate_orbit_trail(volume, cx, cy, cz, t, trail_length=50):
    """Generate a faint orbital trail behind Earth"""
    trail_color = (100, 100, 200)
    
    for i in range(trail_length):
        trail_t = t - (i / trail_length) * 0.5
        trail_x = cx + int(ORBIT_RADIUS * np.cos(trail_t))
        trail_z = cz + int(ORBIT_RADIUS * np.sin(trail_t))
        
        alpha = max(0, 1.0 - (i / trail_length))
        if alpha > 0.1:
            faded_color = tuple(int(c * alpha * 0.3) for c in trail_color)
            add_voxel(volume, trail_x, cy, trail_z, faded_color)

def generate_scene(volume, t):
    """Generate complete solar system scene"""
    # Generate Sun at center
    generate_sun(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    
    # Calculate Earth position (orbital motion)
    earth_x = CENTER_X + int(ORBIT_RADIUS * np.cos(t))
    earth_z = CENTER_Z + int(ORBIT_RADIUS * np.sin(t))
    earth_y = CENTER_Y + int(3 * np.sin(t * 0.1))  # Slight vertical oscillation
    
    # Calculate Earth rotation (spinning on axis)
    earth_rotation = t * EARTH_ROTATION_SPEED
    
    # Generate orbital trail
    generate_orbit_trail(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    
    # Generate Earth
    generate_earth(volume, earth_x, earth_y, earth_z, earth_rotation, t)

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

# Generate animation frames
for frame in tqdm(range(FRAMES), desc="Generating Earth orbit"):
    volume = np.zeros((SIZE, SIZE, SIZE, 4), dtype=np.uint8)
    t = (frame / FRAMES) * 2 * np.pi  # Complete orbit over animation duration
    generate_scene(volume, t)
    enc.encode(splv.Frame(volume, lrAxis="x", udAxis="y", fbAxis="z"))

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

Next steps

Adjust ORBIT_RADIUS to change Earth's distance from the Sun
Modify EARTH_ROTATION_SPEED to change day/night cycle speed
Add more planets by duplicating the Earth generation with different parameters
Experiment with SECONDS to create longer or shorter orbital periods
Try adding a moon by creating a smaller sphere orbiting Earth
Enhance the terrain generation by tweaking the noise_3d function parameters

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