Compass - 3D Voxel Animation Tutorial

This guide walks you through how to generate a looping 3D voxel animation of a compass using SpatialStudio. The script creates a detailed magnetic compass with a spinning needle, rotating dial, and glowing effects 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 realistic compass with:
- A circular brass-colored base
- Cardinal direction markings (N, S, E, W)
- A red magnetic needle that spins and oscillates
- A transparent glass cover with reflections
- Glowing effects around the needle
Animates the needle rotating and wobbling for 8 seconds at 30 FPS
Outputs the file compass.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).
Compass base A circular platform drawn with brass/bronze colors and textured edges.
Direction markers Cardinal points (N, S, E, W) are placed around the compass face with distinct colors.
Magnetic needle A red arrow that rotates smoothly while slightly wobbling to simulate magnetic interference.
Glass cover Semi-transparent voxels with white highlights create a realistic glass dome effect.
Animation loop A normalized time variable t cycles from 0 → 2π, making the needle 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 compass.py and run:

python compass.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/compass.splv"

# Compass settings
COMPASS_RADIUS = 20
BASE_HEIGHT = 6
NEEDLE_LENGTH = 15
GLASS_HEIGHT = 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_compass_base(volume, cx, cy, cz, t):
    brass_color = (205, 127, 50)
    dark_brass = (160, 100, 40)
    
    for dx in range(-COMPASS_RADIUS, COMPASS_RADIUS+1):
        for dz in range(-COMPASS_RADIUS, COMPASS_RADIUS+1):
            distance = np.sqrt(dx*dx + dz*dz)
            if distance <= COMPASS_RADIUS:
                for dy in range(BASE_HEIGHT):
                    # Add texture variation
                    texture = np.sin(dx*0.3 + dz*0.2 + t*0.1) * 0.2
                    if distance > COMPASS_RADIUS - 2:  # Outer ring
                        color = dark_brass
                    else:
                        brightness = 1.0 + texture
                        color = tuple(min(255, int(c * brightness)) for c in brass_color)
                    add_voxel(volume, cx+dx, cy-dy, cz+dz, color)

def generate_direction_markers(volume, cx, cy, cz, t):
    markers = [
        ("N", (255, 255, 255), 0),      # North - White
        ("E", (200, 200, 200), np.pi/2), # East - Light Gray  
        ("S", (180, 180, 180), np.pi),   # South - Gray
        ("W", (200, 200, 200), 3*np.pi/2) # West - Light Gray
    ]
    
    marker_radius = COMPASS_RADIUS - 4
    for letter, color, angle in markers:
        mx = cx + int(marker_radius * np.cos(angle))
        mz = cz + int(marker_radius * np.sin(angle))
        
        # Draw simple letter markers (simplified as small blocks)
        for dx in range(-1, 2):
            for dz in range(-1, 2):
                for dy in range(2):
                    add_voxel(volume, mx+dx, cy+dy+1, mz+dz, color)

def generate_needle(volume, cx, cy, cz, t):
    # Needle rotates with slight wobble
    needle_angle = t * 0.5 + np.sin(t * 3) * 0.1
    wobble = np.sin(t * 4) * 0.05
    
    red_color = (255, 0, 0)
    dark_red = (180, 0, 0)
    white_color = (255, 255, 255)
    
    # Draw needle shaft
    for i in range(-NEEDLE_LENGTH, NEEDLE_LENGTH+1):
        progress = i / NEEDLE_LENGTH
        nx = cx + int(i * np.cos(needle_angle + wobble))
        nz = cz + int(i * np.sin(needle_angle + wobble))
        ny = cy + 2
        
        # Red end (North-pointing)
        if i > 0:
            intensity = 1.0 - (progress * 0.3)
            color = tuple(int(c * intensity) for c in red_color)
            add_voxel(volume, nx, ny, nz, color)
            # Add thickness
            add_voxel(volume, nx, ny+1, nz, color)
        # White end (South-pointing)  
        elif i < 0:
            add_voxel(volume, nx, ny, nz, white_color)
            add_voxel(volume, nx, ny+1, nz, white_color)
        # Center pivot
        else:
            add_voxel(volume, nx, ny, nz, dark_red)
            add_voxel(volume, nx, ny+1, nz, dark_red)

def generate_needle_glow(volume, cx, cy, cz, t):
    # Subtle glow around the needle tip
    needle_angle = t * 0.5 + np.sin(t * 3) * 0.1
    wobble = np.sin(t * 4) * 0.05
    
    # North tip glow
    tip_x = cx + int(NEEDLE_LENGTH * np.cos(needle_angle + wobble))
    tip_z = cz + int(NEEDLE_LENGTH * np.sin(needle_angle + wobble))
    tip_y = cy + 3
    
    glow_color = (255, 100, 100)
    for dx in range(-2, 3):
        for dy in range(-1, 2):
            for dz in range(-2, 3):
                distance = np.sqrt(dx*dx + dy*dy + dz*dz)
                if distance <= 2:
                    alpha = int(80 * (1 - distance/2))
                    add_voxel(volume, tip_x+dx, tip_y+dy, tip_z+dz, glow_color, alpha)

def generate_glass_cover(volume, cx, cy, cz, t):
    glass_color = (200, 220, 255)
    highlight_color = (255, 255, 255)
    
    for dx in range(-COMPASS_RADIUS+2, COMPASS_RADIUS-1):
        for dz in range(-COMPASS_RADIUS+2, COMPASS_RADIUS-1):
            distance = np.sqrt(dx*dx + dz*dz)
            if COMPASS_RADIUS-6 <= distance <= COMPASS_RADIUS-3:
                for dy in range(GLASS_HEIGHT):
                    y_pos = cy + dy + 1
                    # Glass walls
                    alpha = 60 if dy < GLASS_HEIGHT-1 else 40
                    add_voxel(volume, cx+dx, y_pos, cz+dz, glass_color, alpha)
                    
                    # Add highlights
                    if dy == GLASS_HEIGHT-2 and distance > COMPASS_RADIUS-5:
                        highlight_intensity = int(np.sin(dx*0.2 + dz*0.1 + t*0.3) * 30 + 50)
                        add_voxel(volume, cx+dx, y_pos, cz+dz, highlight_color, highlight_intensity)

def generate_compass_face(volume, cx, cy, cz, t):
    face_color = (240, 230, 210)
    line_color = (100, 100, 100)
    
    # Draw compass face with degree markings
    for dx in range(-COMPASS_RADIUS+5, COMPASS_RADIUS-4):
        for dz in range(-COMPASS_RADIUS+5, COMPASS_RADIUS-4):
            distance = np.sqrt(dx*dx + dz*dz)
            if distance <= COMPASS_RADIUS-5:
                add_voxel(volume, cx+dx, cy+1, cz+dz, face_color)
                
                # Add degree lines
                angle = np.arctan2(dz, dx)
                if int(angle * 180/np.pi) % 30 == 0 and distance > COMPASS_RADIUS-8:
                    add_voxel(volume, cx+dx, cy+1, cz+dz, line_color)

def generate_scene(volume, t):
    generate_compass_base(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_compass_face(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_direction_markers(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_needle(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_needle_glow(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_glass_cover(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 compass"):
    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 NEEDLE_LENGTH to make the compass needle longer or shorter.
Modify needle_angle calculation to change rotation speed.
Add more detailed cardinal markings by expanding generate_direction_markers().
Experiment with different brass_color values for unique compass styles.
Increase wobble intensity to simulate stronger magnetic interference.

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