Sun - 3D Voxel Animation Learning Example

This guide walks you through how to generate a looping 3D voxel animation of the sun using SpatialStudio. The script creates a glowing, pulsating sun with solar flares, corona effects, and dynamic surface textures 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 1 radiant sun with:
- A spherical voxel core with animated surface textures
- Pulsating glow effects that change brightness over time
- Dynamic solar flares extending outward
- A shimmering corona atmosphere
Animates the sun burning and glowing for 8 seconds at 30 FPS
Outputs the file sun.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 core The main body is drawn as a sphere with noise-based surface variations to simulate solar activity.
Glow layers Multiple transparent layers around the core create a realistic atmospheric glow effect.
Solar flares Random flame-like extensions shoot outward from the surface, animated with sine waves.
Corona effect A subtle outer atmosphere with particle-like sparkles that shimmer and fade.
Animation loop A normalized time variable t cycles from 0 → 2π, making the pulsing and flares loop 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 sun.py and run:

python sun.py

Full Script

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

# Scene setup
SIZE, FPS, SECONDS = 128, 30, 8
FRAMES = FPS * SECONDS
CENTER_X = CENTER_Y = CENTER_Z = SIZE // 2
OUT_PATH = "../outputs/sun.splv"

# Sun settings
SUN_RADIUS = 25
GLOW_RADIUS = 35
CORONA_RADIUS = 45
FLARE_COUNT = 12

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 generate_sun_core(volume, cx, cy, cz, t):
    core_colors = [(255, 200, 0), (255, 150, 0), (255, 100, 0)]
    
    for dx in range(-SUN_RADIUS, SUN_RADIUS+1):
        for dy in range(-SUN_RADIUS, SUN_RADIUS+1):
            for dz in range(-SUN_RADIUS, SUN_RADIUS+1):
                distance = np.sqrt(dx*dx + dy*dy + dz*dz)
                if distance <= SUN_RADIUS:
                    # Surface noise for solar activity
                    noise = np.sin(dx*0.2 + t*2) * np.cos(dy*0.2 + t*1.5) * np.sin(dz*0.2 + t*2.2)
                    surface_variance = int(noise * 3)
                    
                    # Pulsating brightness
                    pulse = 0.8 + 0.2 * np.sin(t * 3.0)
                    
                    # Color based on distance from center
                    color_index = min(2, int(distance / SUN_RADIUS * 3))
                    base_color = core_colors[color_index]
                    
                    # Apply brightness variation
                    final_color = tuple(min(255, int(c * pulse * (1 + surface_variance * 0.1))) for c in base_color)
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, final_color)

def generate_glow_layer(volume, cx, cy, cz, t):
    glow_color = (255, 200, 100)
    
    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):
                distance = np.sqrt(dx*dx + dy*dy + dz*dz)
                if SUN_RADIUS < distance <= GLOW_RADIUS:
                    # Glow intensity decreases with distance
                    intensity = 1.0 - ((distance - SUN_RADIUS) / (GLOW_RADIUS - SUN_RADIUS))
                    
                    # Pulsating glow
                    pulse = 0.6 + 0.4 * np.sin(t * 2.5 + distance * 0.1)
                    
                    alpha = int(intensity * pulse * 120)
                    if alpha > 10:  # Only add visible glow
                        add_voxel(volume, cx+dx, cy+dy, cz+dz, glow_color, alpha)

def generate_solar_flares(volume, cx, cy, cz, t):
    flare_color = (255, 180, 0)
    
    for i in range(FLARE_COUNT):
        # Flare direction
        angle_xy = (i / FLARE_COUNT) * 2 * np.pi
        angle_z = np.sin(i * 0.7) * 0.5
        
        # Flare animation
        flare_length = SUN_RADIUS + int(15 * np.sin(t * 1.5 + i * 0.5) + 10)
        
        # Generate flare particles
        for length in range(SUN_RADIUS + 2, flare_length):
            # Flare gets thinner as it extends
            thickness = max(1, 4 - int((length - SUN_RADIUS) / 8))
            
            base_x = cx + int(length * np.cos(angle_xy) * np.cos(angle_z))
            base_y = cy + int(length * np.sin(angle_xy) * np.cos(angle_z))
            base_z = cz + int(length * np.sin(angle_z))
            
            # Add thickness to flare
            for tx in range(-thickness, thickness+1):
                for ty in range(-thickness, thickness+1):
                    if tx*tx + ty*ty <= thickness*thickness:
                        # Flare intensity decreases with distance
                        intensity = 1.0 - ((length - SUN_RADIUS) / (flare_length - SUN_RADIUS))
                        alpha = int(intensity * 180)
                        
                        if alpha > 20:
                            add_voxel(volume, base_x+tx, base_y+ty, base_z, flare_color, alpha)

def generate_corona(volume, cx, cy, cz, t):
    corona_color = (255, 255, 200)
    
    # Sparse corona particles
    particle_count = int(200 + 50 * np.sin(t * 2.0))
    
    for i in range(particle_count):
        # Random positions around the sun
        angle = (i / particle_count) * 4 * np.pi + t * 0.5
        radius = GLOW_RADIUS + np.random.random() * (CORONA_RADIUS - GLOW_RADIUS)
        
        x = cx + int(radius * np.cos(angle) * np.sin(i * 0.7))
        y = cy + int(radius * np.sin(angle) * np.sin(i * 0.7))
        z = cz + int(radius * np.cos(i * 0.7))
        
        # Twinkling effect
        twinkle = np.sin(t * 4.0 + i * 0.3) * 0.5 + 0.5
        alpha = int(twinkle * 80)
        
        if alpha > 15:
            add_voxel(volume, x, y, z, corona_color, alpha)

def generate_sun_scene(volume, t):
    generate_sun_core(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_glow_layer(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_solar_flares(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_corona(volume, CENTER_X, CENTER_Y, CENTER_Z, 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 sun"):
    volume = np.zeros((SIZE, SIZE, SIZE, 4), dtype=np.uint8)
    t = (frame / FRAMES) * 2*np.pi
    generate_sun_scene(volume, t)
    enc.encode(splv.Frame(volume, lrAxis="x", udAxis="y", fbAxis="z"))

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

Next steps

Adjust SUN_RADIUS to make the sun bigger or smaller.
Change FLARE_COUNT to add more or fewer solar flares.
Modify the core_colors array to create different colored stars (blue giant, red dwarf, etc.).
Add rotation by incrementing angles based on frame number.
Experiment with different noise functions for more realistic surface textures.

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