Campfire - 3D Voxel Animation Learning Example

This guide walks you through how to generate a looping 3D voxel animation of a campfire using SpatialStudio. The script creates a realistic campfire with flickering flames, glowing embers, and crackling logs 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 campfire with:
- A ring of brown wooden logs
- Dancing orange and red flames
- Floating yellow embers and sparks
- A bed of glowing coals at the base
Animates the flames flickering and embers rising for 8 seconds at 30 FPS
Outputs the file campfire.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).
Log ring Brown cylindrical logs are arranged in a circle as the campfire base.
Flames Orange and red flames are drawn as elongated shapes with noise-based flickering motion.
Embers Small yellow and orange particles float upward with random drift patterns.
Coals Dark red glowing voxels form the fire bed between the logs.
Animation loop A normalized time variable t cycles from 0 → 2π, making flames dance and embers rise continuously.
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 campfire.py and run:

python campfire.py

Full Script

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

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

# Campfire settings
LOG_RADIUS = 20
LOG_COUNT = 6
FLAME_HEIGHT = 25
EMBER_COUNT = 15

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_logs(volume, cx, cy, cz, t):
    log_color = (101, 67, 33)  # Dark brown
    log_end_color = (139, 90, 43)  # Lighter brown for ends
    
    for i in range(LOG_COUNT):
        angle = (i / LOG_COUNT) * 2 * np.pi
        log_x = cx + int(LOG_RADIUS * np.cos(angle))
        log_z = cz + int(LOG_RADIUS * np.sin(angle))
        log_y = cy - 8
        
        # Draw log body
        for dx in range(-12, 13):
            for dy in range(-3, 4):
                for dz in range(-3, 4):
                    if dy*dy + dz*dz <= 9:  # Cylindrical shape
                        noise = int(np.sin(dx*0.3 + dy*0.5 + t) * 1.5)
                        final_x = log_x + int(dx * np.cos(angle)) + noise
                        final_z = log_z + int(dx * np.sin(angle))
                        final_y = log_y + dy
                        
                        # Use darker color for log ends
                        color = log_end_color if abs(dx) > 8 else log_color
                        add_voxel(volume, final_x, final_y, final_z, color)

def generate_coals(volume, cx, cy, cz, t):
    coal_colors = [(139, 0, 0), (178, 34, 34), (255, 69, 0)]  # Dark to bright red
    
    for x in range(cx-15, cx+16):
        for z in range(cz-15, cz+16):
            dist = np.sqrt((x-cx)**2 + (z-cz)**2)
            if dist < 12 and random.random() < 0.4:
                glow_intensity = np.sin(t * 3 + x*0.1 + z*0.1) * 0.5 + 0.5
                color_idx = min(2, int(glow_intensity * 3))
                color = coal_colors[color_idx]
                add_voxel(volume, x, cy-10, z, color)

def generate_flames(volume, cx, cy, cz, t):
    flame_colors = [
        (255, 0, 0),    # Red base
        (255, 69, 0),   # Orange-red
        (255, 140, 0),  # Dark orange
        (255, 165, 0),  # Orange
        (255, 215, 0),  # Gold
    ]
    
    # Generate multiple flame tongues
    for flame_id in range(8):
        base_angle = (flame_id / 8) * 2 * np.pi
        flame_base_x = cx + int(8 * np.cos(base_angle))
        flame_base_z = cz + int(8 * np.sin(base_angle))
        
        # Flame height varies with time and position
        height_variation = np.sin(t * 4 + flame_id * 0.8) * 8
        current_height = FLAME_HEIGHT + int(height_variation)
        
        for h in range(current_height):
            # Flame gets narrower as it goes up
            width = max(1, int(6 * (1 - h / current_height)))
            
            # Add flickering motion
            flicker_x = int(np.sin(t * 6 + h * 0.3 + flame_id) * (h * 0.2))
            flicker_z = int(np.cos(t * 5 + h * 0.2 + flame_id) * (h * 0.15))
            
            flame_x = flame_base_x + flicker_x
            flame_z = flame_base_z + flicker_z
            flame_y = cy - 5 + h
            
            # Color changes with height (red at bottom, yellow at top)
            color_progress = h / current_height
            color_idx = min(4, int(color_progress * 5))
            flame_color = flame_colors[color_idx]
            
            # Draw flame cross-section
            for dx in range(-width, width+1):
                for dz in range(-width, width+1):
                    if dx*dx + dz*dz <= width*width:
                        if random.random() < 0.7:  # Some transparency effect
                            add_voxel(volume, flame_x+dx, flame_y, flame_z+dz, flame_color)

def generate_embers(volume, cx, cy, cz, t):
    ember_colors = [(255, 215, 0), (255, 140, 0), (255, 69, 0)]  # Gold to orange
    
    random.seed(42)  # Consistent ember positions
    for i in range(EMBER_COUNT):
        # Each ember has its own movement pattern
        base_x = random.randint(cx-15, cx+15)
        base_z = random.randint(cz-15, cz+15)
        
        # Embers rise and drift
        rise_speed = 2 + random.random() * 3
        drift_x = np.sin(t * 2 + i * 0.5) * 8
        drift_z = np.cos(t * 1.5 + i * 0.3) * 6
        
        ember_x = base_x + int(drift_x)
        ember_y = cy + int((t * rise_speed + i * 3) % 40) - 10
        ember_z = base_z + int(drift_z)
        
        # Ember brightness flickers
        brightness = np.sin(t * 8 + i * 1.2) * 0.3 + 0.7
        color_idx = min(2, int(brightness * 3))
        ember_color = ember_colors[color_idx]
        
        # Small glowing particle
        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, ember_x+dx, ember_y+dy, ember_z+dz, ember_color)

def generate_smoke(volume, cx, cy, cz, t):
    smoke_color = (105, 105, 105)  # Gray smoke
    
    for i in range(5):
        # Smoke particles rise and spread
        smoke_x = cx + int(np.sin(t * 0.5 + i) * 15)
        smoke_y = cy + 20 + int(t * 8 + i * 5) % 30
        smoke_z = cz + int(np.cos(t * 0.3 + i) * 12)
        
        # Smoke dissipates as it rises
        opacity = max(0, 1 - ((smoke_y - cy - 20) / 30))
        if opacity > 0 and random.random() < opacity * 0.3:
            add_voxel(volume, smoke_x, smoke_y, smoke_z, smoke_color)

def generate_scene(volume, t):
    generate_logs(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_coals(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_flames(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_embers(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    generate_smoke(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 campfire"):
    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 FLAME_HEIGHT to make taller or shorter flames.
Increase EMBER_COUNT for more floating sparks.
Modify flame_colors to create blue or green magical flames.
Add wind effects by changing the flicker patterns.
Experiment with LOG_COUNT and LOG_RADIUS for different campfire sizes.

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