Inner Planets Orbit - 3D Voxel Animation

This guide walks you through how to generate a looping 3D voxel animation of the inner planets orbiting the Sun using SpatialStudio. The script creates a realistic solar system model showing Mercury, Venus, Earth, and Mars in their orbital paths around a glowing Sun 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 the Sun at the center with:
- A bright yellow-orange glowing sphere
- Subtle surface texture variations
- Radial light emission effects
Animates 4 inner planets (Mercury, Venus, Earth, Mars) with:
- Accurate relative sizes and colors
- Elliptical orbital paths at different speeds
- Individual rotation on their axes
Runs for 12 seconds at 24 FPS showing multiple orbital cycles
Outputs the file inner_planets_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).
Central Sun The Sun is drawn as a large sphere with animated surface patterns and a bright glow effect.
Planet orbits Each planet follows an elliptical path calculated using trigonometric functions, with Mercury orbiting fastest and Mars slowest.
Planet rendering Planets are drawn as textured spheres with realistic colors (gray Mercury, bright Venus, blue-green Earth, red Mars).
Animation timing A normalized time variable t cycles from 0 → 2π, with each planet having different orbital periods for realistic motion.
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 inner_planets_orbit.py and run:

python inner_planets_orbit.py

Full Script

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

# Scene setup
SIZE, FPS, SECONDS = 128, 24, 12
FRAMES = FPS * SECONDS
CENTER_X = CENTER_Y = CENTER_Z = SIZE // 2
OUT_PATH = "../outputs/inner_planets_orbit.splv"

# Solar system settings
SUN_RADIUS = 8
PLANET_DATA = [
    {"name": "Mercury", "radius": 2, "orbit_radius": 18, "speed": 4.0, "color": (169, 169, 169)},
    {"name": "Venus", "radius": 3, "orbit_radius": 25, "speed": 1.6, "color": (255, 198, 73)},
    {"name": "Earth", "radius": 3, "orbit_radius": 32, "speed": 1.0, "color": (100, 149, 237)},
    {"name": "Mars", "radius": 2, "orbit_radius": 40, "speed": 0.5, "color": (205, 92, 92)}
]

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 generate_sun(volume, cx, cy, cz, t):
    sun_color = (255, 215, 0)
    glow_color = (255, 165, 0)
    
    # Main sun body with surface texture
    for dx in range(-SUN_RADIUS-2, SUN_RADIUS+3):
        for dy in range(-SUN_RADIUS-2, SUN_RADIUS+3):
            for dz in range(-SUN_RADIUS-2, SUN_RADIUS+3):
                distance = np.sqrt(dx*dx + dy*dy + dz*dz)
                
                # Sun core
                if distance <= SUN_RADIUS:
                    surface_var = np.sin(dx*0.4 + t*2) * np.cos(dy*0.3 + t*1.5) * np.sin(dz*0.5 + t*1.8)
                    brightness = 1.0 + surface_var * 0.2
                    final_color = tuple(min(255, int(c * brightness)) for c in sun_color)
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, final_color)
                
                # Sun glow effect
                elif distance <= SUN_RADIUS + 2:
                    glow_intensity = 1.0 - (distance - SUN_RADIUS) / 2.0
                    glow_final = tuple(int(c * glow_intensity * 0.6) for c in glow_color)
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, glow_final)

def generate_planet(volume, cx, cy, cz, radius, color, t, rotation_speed=1.0):
    for dx in range(-radius-1, radius+2):
        for dy in range(-radius-1, radius+2):
            for dz in range(-radius-1, radius+2):
                distance = np.sqrt(dx*dx + dy*dy + dz*dz)
                
                if distance <= radius:
                    # Add surface texture based on planet rotation
                    texture = np.sin(dx*0.5 + t*rotation_speed) * np.cos(dy*0.3) * np.sin(dz*0.4 + t*rotation_speed*0.7)
                    brightness = 0.8 + texture * 0.3
                    
                    # Add some shading based on distance from center
                    shade = 1.0 - (distance / radius) * 0.2
                    brightness *= shade
                    
                    final_color = tuple(max(0, min(255, int(c * brightness))) for c in color)
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, final_color)

def generate_orbital_system(volume, t):
    # Generate the Sun
    generate_sun(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    
    # Generate each planet in its orbit
    for planet in PLANET_DATA:
        # Calculate orbital position
        angle = t * planet["speed"]
        
        # Add slight elliptical orbit variation
        orbit_variation = planet["orbit_radius"] + np.sin(angle * 2) * 2
        
        # Calculate 3D position (orbiting in XZ plane with slight Y variation)
        px = CENTER_X + int(orbit_variation * np.cos(angle))
        py = CENTER_Y + int(np.sin(angle * 0.3) * 3)  # Slight vertical variation
        pz = CENTER_Z + int(orbit_variation * np.sin(angle))
        
        # Generate the planet with its own rotation
        generate_planet(volume, px, py, pz, planet["radius"], planet["color"], t, planet["speed"]*2)

def add_orbit_trails(volume, t):
    trail_color = (50, 50, 50)
    
    # Draw faint orbital paths
    for planet in PLANET_DATA:
        radius = planet["orbit_radius"]
        for i in range(0, 360, 8):  # Every 8 degrees
            angle = np.radians(i)
            x = CENTER_X + int(radius * np.cos(angle))
            z = CENTER_Z + int(radius * np.sin(angle))
            
            # Only show trail occasionally for visual clarity
            if (int(t*10) + i) % 32 < 4:
                add_voxel(volume, x, CENTER_Y, z, trail_color)

def generate_scene(volume, t):
    add_orbit_trails(volume, t)
    generate_orbital_system(volume, 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 inner planets orbit"):
    volume = np.zeros((SIZE, SIZE, SIZE, 4), dtype=np.uint8)
    t = (frame / FRAMES) * 2*np.pi
    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 PLANET_DATA to modify orbital speeds, sizes, or colors
Add asteroid belt by creating small rocks between Mars and Jupiter's orbit
Include planet moons (like Earth's Moon) with their own sub-orbits
Experiment with different orbital inclinations by modifying the Y-axis calculations
Add starfield background by sprinkling white pixels in the distant volume
Increase SECONDS to show longer orbital periods and planet alignments

Educational notes

This animation demonstrates several astronomical concepts:

Orbital mechanics: Inner planets orbit faster than outer ones (Kepler's laws)
Relative sizes: Planets are scaled proportionally to show size differences
Rotation periods: Each planet spins on its axis while orbiting
Solar dominance: The Sun's size and brightness show its gravitational influence

The animation completes multiple Mercury orbits while Mars barely completes one, accurately representing the relative orbital periods of our solar system's inner planets.

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