Carousel Animation - 3D Voxel Learning Example

This guide walks you through how to generate a looping 3D voxel animation of a carousel using SpatialStudio. The script creates a colorful rotating carousel with horses that bob up and down 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
Builds a rotating carousel with:
- A circular platform base
- 6 carousel horses in different colors
- Vertical support poles for each horse
- A decorative top canopy
Animates smooth rotation and horse bobbing motion for 8 seconds at 30 FPS
Outputs the file carousel.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).
Carousel base A circular platform is drawn using distance calculations from the center point.
Horses Simple voxel horses are positioned around the carousel perimeter, each with unique colors.
Rotation system All carousel elements rotate around the center axis using trigonometric functions.
Bobbing motion Horses move up and down independently using sine waves with different phase offsets.
Animation loop A normalized time variable t cycles from 0 → 2π, ensuring the motion 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 carousel.py and run:

python carousel.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/carousel.splv"

# Carousel settings
HORSE_COUNT = 6
CAROUSEL_RADIUS = 35
PLATFORM_RADIUS = 45
PLATFORM_HEIGHT = 4
HORSE_HEIGHT = 12

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_platform(volume, cx, cy, cz):
    platform_color = (139, 69, 19)  # Brown wood
    edge_color = (160, 82, 45)      # Lighter brown edge
    
    for dx in range(-PLATFORM_RADIUS, PLATFORM_RADIUS+1):
        for dz in range(-PLATFORM_RADIUS, PLATFORM_RADIUS+1):
            dist = np.sqrt(dx*dx + dz*dz)
            if dist <= PLATFORM_RADIUS:
                for dy in range(PLATFORM_HEIGHT):
                    color = edge_color if dist > PLATFORM_RADIUS-2 else platform_color
                    add_voxel(volume, cx+dx, cy-dy, cz+dz, color)

def generate_horse(volume, cx, cy, cz, color):
    # Horse body (simplified rectangular shape)
    body_width, body_height, body_length = 4, 3, 8
    
    # Body
    for dx in range(-body_width//2, body_width//2+1):
        for dy in range(body_height):
            for dz in range(-body_length//2, body_length//2+1):
                add_voxel(volume, cx+dx, cy+dy, cz+dz, color)
    
    # Head
    head_color = tuple(max(0, c-20) for c in color)  # Slightly darker
    for dx in range(-2, 3):
        for dy in range(2, 6):
            for dz in range(3, 7):
                if dx*dx + (dy-3)*(dy-3) + (dz-4)*(dz-4) <= 4:
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, head_color)
    
    # Legs
    leg_color = tuple(max(0, c-30) for c in color)  # Darker for legs
    leg_positions = [(-2, -6), (2, -6), (-2, 2), (2, 2)]
    for lx, lz in leg_positions:
        for dy in range(-6, 0):
            add_voxel(volume, cx+lx, cy+dy, cz+lz, leg_color)

def generate_pole(volume, cx, cy, cz):
    pole_color = (192, 192, 192)  # Silver
    pole_height = 20
    
    for dy in range(-pole_height, HORSE_HEIGHT+5):
        add_voxel(volume, cx, cy+dy, cz, pole_color)
        # Add some thickness
        add_voxel(volume, cx+1, cy+dy, cz, pole_color)
        add_voxel(volume, cx, cy+dy, cz+1, pole_color)

def generate_canopy(volume, cx, cy, cz):
    canopy_color = (255, 215, 0)    # Gold
    stripe_color = (220, 20, 60)    # Crimson stripes
    canopy_radius = PLATFORM_RADIUS + 5
    
    for dx in range(-canopy_radius, canopy_radius+1):
        for dz in range(-canopy_radius, canopy_radius+1):
            dist = np.sqrt(dx*dx + dz*dz)
            if dist <= canopy_radius:
                # Create striped pattern
                angle = np.arctan2(dz, dx)
                stripe_index = int((angle + np.pi) / (np.pi/8)) % 2
                color = stripe_color if stripe_index else canopy_color
                
                for dy in range(2):
                    add_voxel(volume, cx+dx, cy+25+dy, cz+dz, color)

def generate_carousel(volume, cx, cy, cz, t):
    horse_colors = [
        (255, 182, 193),  # Light pink
        (135, 206, 250),  # Light blue
        (144, 238, 144),  # Light green
        (255, 218, 185),  # Peach
        (221, 160, 221),  # Plum
        (255, 255, 224),  # Light yellow
    ]
    
    # Generate platform
    generate_platform(volume, cx, cy, cz)
    
    # Generate canopy
    generate_canopy(volume, cx, cy, cz)
    
    # Generate horses and poles
    for i in range(HORSE_COUNT):
        # Base angle for this horse
        base_angle = (i / HORSE_COUNT) * 2 * np.pi
        
        # Add rotation over time
        angle = base_angle + t * 0.5  # Rotate slowly
        
        # Position around carousel
        horse_x = cx + int(CAROUSEL_RADIUS * np.cos(angle))
        horse_z = cz + int(CAROUSEL_RADIUS * np.sin(angle))
        
        # Bobbing motion (each horse has different phase)
        bob_offset = np.sin(t * 2.0 + i * np.pi/3) * 4
        horse_y = cy + 8 + int(bob_offset)
        
        # Generate pole
        generate_pole(volume, horse_x, cy, horse_z)
        
        # Generate horse
        color = horse_colors[i % len(horse_colors)]
        generate_horse(volume, horse_x, horse_y, horse_z, color)

def generate_decorative_lights(volume, cx, cy, cz, t):
    light_colors = [(255, 255, 0), (255, 0, 255), (0, 255, 255)]  # Yellow, Magenta, Cyan
    light_radius = PLATFORM_RADIUS - 5
    
    for i in range(12):  # 12 lights around the edge
        angle = (i / 12) * 2 * np.pi + t * 1.0  # Lights rotate faster
        lx = cx + int(light_radius * np.cos(angle))
        lz = cz + int(light_radius * np.sin(angle))
        ly = cy + 10
        
        # Twinkling effect
        brightness = 0.7 + 0.3 * np.sin(t * 3.0 + i * 0.5)
        color = light_colors[i % len(light_colors)]
        final_color = tuple(int(c * brightness) for c in color)
        
        # Add light voxel
        for dx in range(-1, 2):
            for dy in range(-1, 2):
                for dz in range(-1, 2):
                    if dx*dx + dy*dy + dz*dz <= 1:
                        add_voxel(volume, lx+dx, ly+dy, lz+dz, final_color)

def generate_scene(volume, t):
    generate_carousel(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_decorative_lights(volume, CENTER_X, CENTER_Y, CENTER_Z, t)

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

for frame in tqdm(range(FRAMES), desc="Generating carousel"):
    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

Change HORSE_COUNT to add more horses to your carousel.
Edit horse_colors for different horse appearances.
Modify rotation speed by changing the multiplier in angle = base_angle + t * 0.5.
Add more decorative elements like flags or banners.
Experiment with different bobbing patterns by adjusting the sine wave parameters.
Try changing CAROUSEL_RADIUS to make a larger or smaller carousel.

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