Coral Reef - 3D Voxel Animation Learning Example

This guide walks you through how to generate a looping 3D voxel animation of a coral reef using SpatialStudio. The script creates a vibrant underwater scene with swaying corals, swimming fish, and floating bubbles 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 a diverse coral reef with:
- Multiple coral formations (brain coral, fan coral, tube coral)
- Schools of colorful fish swimming in patterns
- Rising air bubbles
- Swaying seaweed and kelp
Animates the underwater ecosystem for 10 seconds at 30 FPS
Outputs the file coral_reef.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).
Coral formations Different coral types are generated using mathematical functions - spherical clusters for brain coral, branching structures for fan coral, and cylindrical tubes.
Swimming fish Small fish move in circular and figure-8 patterns around the reef using trigonometric functions.
Bubbles Transparent bubbles rise from the sea floor with slight horizontal drift and size variations.
Sea floor Sandy bottom with scattered rocks and debris for realistic depth.
Animation loop A normalized time variable t cycles from 0 → 2π, ensuring smooth looping motion for all elements.
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 coral_reef.py and run:

python coral_reef.py

Full Script

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

# Scene setup
SIZE, FPS, SECONDS = 128, 30, 10
FRAMES = FPS * SECONDS
CENTER_X = CENTER_Y = CENTER_Z = SIZE // 2
OUT_PATH = "../outputs/coral_reef.splv"

# Reef settings
CORAL_COUNT = 12
FISH_COUNT = 15
BUBBLE_COUNT = 8

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_sea_floor(volume):
    """Create sandy bottom with rocks"""
    sand_color = (194, 178, 128)
    rock_color = (105, 105, 105)
    
    # Sandy floor
    for x in range(SIZE):
        for z in range(SIZE):
            height = int(3 + 2*np.sin(x*0.1)*np.cos(z*0.1))
            for y in range(height):
                add_voxel(volume, x, y, z, sand_color)
    
    # Scattered rocks
    for _ in range(8):
        rx, rz = np.random.randint(10, SIZE-10, 2)
        rock_size = np.random.randint(3, 7)
        for dx in range(-rock_size, rock_size+1):
            for dy in range(rock_size):
                for dz in range(-rock_size, rock_size+1):
                    if dx*dx + dz*dz <= rock_size*rock_size:
                        add_voxel(volume, rx+dx, 5+dy, rz+dz, rock_color)

def generate_brain_coral(volume, cx, cy, cz, size, color, t):
    """Generate brain coral with wavy surface"""
    for dx in range(-size, size+1):
        for dy in range(-size//2, size+1):
            for dz in range(-size, size+1):
                dist = np.sqrt(dx*dx + dy*dy*1.5 + dz*dz)
                if dist <= size:
                    # Brain coral texture
                    wave = np.sin(dx*0.4 + t*0.5) * np.cos(dz*0.4)
                    if wave > 0.3 or dist > size - 2:
                        brightness = 1.0 + wave * 0.2
                        final_color = tuple(min(255, int(c * brightness)) for c in color)
                        add_voxel(volume, cx+dx, cy+dy, cz+dz, final_color)

def generate_fan_coral(volume, cx, cy, cz, height, color, t):
    """Generate fan-shaped coral that sways"""
    sway = np.sin(t * 1.5) * 2
    for y in range(height):
        fan_width = int((y / height) * 8)
        sway_offset = int(sway * (y / height))
        for dx in range(-fan_width, fan_width+1):
            for dz in range(-2, 3):
                if abs(dx) >= fan_width - 1 or y < 2:  # Create fan shape
                    add_voxel(volume, cx+dx+sway_offset, cy+y, cz+dz, color)

def generate_tube_coral(volume, cx, cy, cz, height, color, t):
    """Generate tube coral clusters"""
    for tube in range(3):
        tube_x = cx + (tube - 1) * 3
        tube_height = height + int(2*np.sin(t + tube))
        for y in range(tube_height):
            radius = 2 if y < tube_height - 3 else 3  # Wider at top
            for dx in range(-radius, radius+1):
                for dz in range(-radius, radius+1):
                    if dx*dx + dz*dz <= radius*radius:
                        if dx*dx + dz*dz >= (radius-1)*(radius-1) or y < 2:
                            add_voxel(volume, tube_x+dx, cy+y, cz+dz, color)

def generate_coral_formations(volume, t):
    """Create various coral formations"""
    coral_colors = [
        (255, 99, 71),   # Tomato red
        (255, 165, 0),   # Orange
        (255, 20, 147),  # Deep pink
        (138, 43, 226),  # Blue violet
        (0, 255, 127),   # Spring green
        (255, 215, 0),   # Gold
    ]
    
    positions = [
        (30, 8, 40), (90, 12, 30), (60, 6, 80), (25, 10, 90),
        (100, 8, 70), (45, 15, 25), (75, 9, 95), (20, 11, 60),
        (95, 7, 45), (55, 13, 15), (35, 9, 75), (80, 14, 85)
    ]
    
    for i, (x, y, z) in enumerate(positions):
        color = coral_colors[i % len(coral_colors)]
        coral_type = i % 3
        
        if coral_type == 0:  # Brain coral
            size = 6 + int(2*np.sin(i*0.5))
            generate_brain_coral(volume, x, y, z, size, color, t)
        elif coral_type == 1:  # Fan coral
            height = 12 + int(3*np.cos(i*0.7))
            generate_fan_coral(volume, x, y, z, height, color, t)
        else:  # Tube coral
            height = 8 + int(2*np.sin(i*0.3))
            generate_tube_coral(volume, x, y, z, height, color, t)

def generate_fish(volume, t):
    """Create swimming fish"""
    fish_colors = [
        (255, 255, 0),   # Yellow tang
        (0, 191, 255),   # Deep sky blue
        (255, 105, 180), # Hot pink
        (50, 205, 50),   # Lime green
        (255, 140, 0),   # Dark orange
    ]
    
    for i in range(FISH_COUNT):
        # Different swimming patterns
        if i % 3 == 0:  # Circular motion
            radius = 25 + 10*np.sin(i*0.5)
            angle = t*1.5 + i*0.8
            fx = CENTER_X + int(radius * np.cos(angle))
            fz = CENTER_Z + int(radius * np.sin(angle))
            fy = 40 + int(8*np.sin(t*2 + i*0.5))
        elif i % 3 == 1:  # Figure-8 pattern
            fx = CENTER_X + int(20*np.sin(t*1.2 + i*0.6))
            fz = CENTER_Z + int(15*np.sin(t*2.4 + i*0.6))
            fy = 30 + int(5*np.cos(t*1.8 + i*0.4))
        else:  # Vertical swimming
            fx = 20 + (i * 8) % (SIZE - 40)
            fz = 30 + int(10*np.sin(t*0.8 + i*0.3))
            fy = 25 + int(15*np.sin(t*1.5 + i*0.7))
        
        # Fish body (simple ellipsoid)
        color = fish_colors[i % len(fish_colors)]
        for dx in range(-2, 3):
            for dy in range(-1, 2):
                for dz in range(-3, 4):
                    if dx*dx + dy*dy*2 + dz*dz*0.5 <= 4:
                        add_voxel(volume, fx+dx, fy+dy, fz+dz, color)

def generate_bubbles(volume, t):
    """Create rising bubbles"""
    for i in range(BUBBLE_COUNT):
        # Bubbles rise and reset
        bubble_cycle = (t*2 + i*0.8) % (2*np.pi)
        rise_height = int((bubble_cycle / (2*np.pi)) * 80)
        
        bx = 20 + (i * 15) % (SIZE - 40) + int(3*np.sin(t*1.5 + i))
        by = 10 + rise_height
        bz = 25 + (i * 12) % (SIZE - 50) + int(2*np.cos(t*1.2 + i))
        
        # Bubble size varies
        bubble_size = 1 + int(np.sin(i*0.5))
        bubble_color = (173, 216, 230)  # Light blue
        
        for dx in range(-bubble_size, bubble_size+1):
            for dy in range(-bubble_size, bubble_size+1):
                for dz in range(-bubble_size, bubble_size+1):
                    if dx*dx + dy*dy + dz*dz <= bubble_size*bubble_size:
                        # Transparent bubbles
                        add_voxel(volume, bx+dx, by+dy, bz+dz, bubble_color, 128)

def generate_seaweed(volume, t):
    """Create swaying seaweed"""
    seaweed_color = (34, 139, 34)  # Forest green
    positions = [(15, 5, 20), (110, 5, 35), (40, 5, 100), (85, 5, 75)]
    
    for px, py, pz in positions:
        sway = np.sin(t*1.8 + px*0.01) * 4
        height = 20
        for y in range(height):
            sway_amount = int(sway * (y / height) * 0.8)
            thickness = 2 if y < height//2 else 1
            for dx in range(-thickness, thickness+1):
                for dz in range(-thickness, thickness+1):
                    add_voxel(volume, px+dx+sway_amount, py+y, pz+dz, seaweed_color)

def generate_scene(volume, t):
    generate_sea_floor(volume)
    generate_coral_formations(volume, t)
    generate_fish(volume, t)
    generate_bubbles(volume, t)
    generate_seaweed(volume, t)

# Set random seed for consistent rock placement
np.random.seed(42)

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

for frame in tqdm(range(FRAMES), desc="Generating coral reef"):
    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 CORAL_COUNT, FISH_COUNT, or BUBBLE_COUNT to modify the reef density.
Edit coral colors in coral_colors for different reef themes.
Add more fish swimming patterns by modifying the motion equations.
Experiment with different coral shapes by creating new generation functions.
Add particle effects like floating plankton or debris.

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