Windmill - 3D Voxel Animation Tutorial

This guide walks you through how to generate a looping 3D voxel animation of a windmill using SpatialStudio. The script creates a classic windmill with rotating blades that spin gracefully 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 windmill structure with:
- A cylindrical stone tower base
- Four wooden rotating blades
- A detailed rooftop cap
- Realistic weathered textures
Animates the blades rotating continuously for 10 seconds at 30 FPS
Outputs the file windmill.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).
Tower base The windmill body is drawn as a tapered cylinder using stone-like gray colors with texture variations.
Rotating blades Four wooden blades rotate around a central hub, with each blade angled for realistic wind-catching geometry.
Rooftop details A conical cap sits atop the tower with darker materials to simulate aged wood or metal.
Animation loop A normalized time variable t cycles from 0 → 2π, making the blade rotation loop seamlessly.
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 windmill.py and run:

python windmill.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/windmill.splv"

# Windmill settings
TOWER_HEIGHT = 45
TOWER_RADIUS = 12
BLADE_LENGTH = 25
BLADE_COUNT = 4

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_tower(volume, cx, cy, cz, t):
    stone_base = (120, 120, 120)
    stone_dark = (90, 90, 90)
    
    for y_offset in range(-TOWER_HEIGHT//2, TOWER_HEIGHT//2):
        # Tower tapers slightly toward the top
        radius_at_height = TOWER_RADIUS - int(abs(y_offset) * 0.1)
        
        for dx in range(-radius_at_height, radius_at_height+1):
            for dz in range(-radius_at_height, radius_at_height+1):
                distance = np.sqrt(dx*dx + dz*dz)
                if distance <= radius_at_height:
                    # Add texture variation
                    noise = np.sin(dx*0.3 + dz*0.3 + y_offset*0.2) * 0.2
                    texture = np.sin(dx*0.8 + dz*0.8 + y_offset*0.1) * 0.1
                    
                    if noise > 0.1:
                        color = stone_dark
                    else:
                        brightness = 1.0 + texture
                        color = tuple(int(c * brightness) for c in stone_base)
                        color = tuple(min(255, max(50, c)) for c in color)
                    
                    add_voxel(volume, cx+dx, cy+y_offset, cz+dz, color)

def generate_blade(volume, cx, cy, cz, angle, blade_id, t):
    wood_color = (139, 69, 19)
    wood_light = (160, 82, 45)
    
    # Calculate blade position
    blade_x = cx + int(BLADE_LENGTH * 0.7 * np.cos(angle))
    blade_z = cz + int(BLADE_LENGTH * 0.7 * np.sin(angle))
    
    # Draw blade from center to tip
    for i in range(BLADE_LENGTH):
        progress = i / BLADE_LENGTH
        
        # Blade gets narrower toward the tip
        width = max(1, int(4 * (1 - progress * 0.8)))
        
        step_x = cx + int(i * np.cos(angle))
        step_z = cz + int(i * np.sin(angle))
        
        for w in range(-width, width+1):
            for h in range(-2, 3):
                # Perpendicular offset for blade thickness
                offset_x = int(w * np.sin(angle))
                offset_z = int(w * -np.cos(angle))
                
                # Wood texture
                grain = np.sin(i*0.2 + w*0.3 + h*0.1) * 0.3
                if grain > 0:
                    color = wood_light
                else:
                    color = wood_color
                
                add_voxel(volume, step_x + offset_x, cy + h, step_z + offset_z, color)

def generate_blades(volume, cx, cy, cz, t):
    hub_color = (80, 60, 40)
    
    # Central hub
    for dx in range(-3, 4):
        for dy in range(-3, 4):
            for dz in range(-3, 4):
                if dx*dx + dy*dy + dz*dz <= 9:
                    add_voxel(volume, cx+dx, cy+dy, cz+dz, hub_color)
    
    # Generate rotating blades
    for i in range(BLADE_COUNT):
        base_angle = (i / BLADE_COUNT) * 2*np.pi
        rotation_angle = base_angle + t * 1.5  # Rotation speed
        generate_blade(volume, cx, cy, cz, rotation_angle, i, t)

def generate_roof(volume, cx, cy, cz, t):
    roof_color = (60, 40, 40)
    roof_highlight = (80, 60, 60)
    
    roof_base_y = cy + TOWER_HEIGHT//2
    roof_height = 12
    
    for y_offset in range(roof_height):
        radius = max(1, TOWER_RADIUS - y_offset)
        
        for dx in range(-radius, radius+1):
            for dz in range(-radius, radius+1):
                if dx*dx + dz*dz <= radius*radius:
                    # Roof shingle texture
                    shingle = (dx + dz + y_offset) % 3
                    color = roof_highlight if shingle == 0 else roof_color
                    
                    add_voxel(volume, cx+dx, roof_base_y+y_offset, cz+dz, color)

def generate_ground(volume, cx, cy, cz):
    grass_color = (34, 139, 34)
    dirt_color = (101, 67, 33)
    
    ground_y = cy - TOWER_HEIGHT//2 - 5
    
    for dx in range(-SIZE//2, SIZE//2):
        for dz in range(-SIZE//2, SIZE//2):
            distance = np.sqrt(dx*dx + dz*dz)
            if distance < SIZE//2:
                # Mix grass and dirt
                noise = np.sin(dx*0.1 + dz*0.1) + np.cos(dx*0.05 + dz*0.08)
                if noise > 0.5:
                    color = grass_color
                else:
                    color = dirt_color
                
                add_voxel(volume, cx+dx, ground_y, cz+dz, color)

def generate_scene(volume, t):
    # Generate windmill components
    generate_ground(volume, CENTER_X, CENTER_Y, CENTER_Z)
    generate_tower(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_roof(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    
    # Blades are positioned at upper part of tower
    blade_y = CENTER_Y + TOWER_HEIGHT//3
    generate_blades(volume, CENTER_X, blade_y, CENTER_Z - TOWER_RADIUS - 5, t)

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

for frame in tqdm(range(FRAMES), desc="Generating windmill"):
    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 BLADE_COUNT to create windmills with different numbers of blades.
Modify the rotation speed by changing the multiplier in t * 1.5.
Add wind effects by making the tower sway slightly with np.sin(t * 0.5) * 2.
Create multiple windmills by calling generate_scene() with different center positions.
Experiment with different materials by changing the color palettes for stone, wood, and roof sections.

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