3D Voxel Animation: Fern

This guide walks you through how to generate a looping 3D voxel animation of a fern using SpatialStudio. The script creates a realistic fern plant that gently sways and grows 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
Generates a procedural fern with:
- A brown woody stem/trunk
- Multiple branching fronds with natural curves
- Gradient green coloring from dark to bright
- Subtle swaying motion in the wind
Animates the fern swaying naturally for 8 seconds at 30 FPS
Outputs the file fern.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).
Stem structure The main trunk is drawn as a vertical brown cylinder that gets thicker toward the base.
Frond generation Fern fronds are created using fractal-like branching patterns, with smaller leaflets growing off main branches.
Natural colors The fern uses a gradient from dark forest green at the base to bright green at the tips of fronds.
Swaying animation A gentle wind effect makes the fronds sway using sine waves, with different frequencies for natural movement.
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 fern.py and run:

python fern.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/fern.splv"

# Fern settings
STEM_HEIGHT = 45
FROND_COUNT = 12
MAX_FROND_LENGTH = 25

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_stem(volume, cx, cy, cz, t):
    stem_color = (101, 67, 33)  # Brown
    sway_base = np.sin(t * 0.8) * 1.5
    
    for i in range(STEM_HEIGHT):
        progress = i / STEM_HEIGHT
        # Stem gets thicker at base and sways more at top
        thickness = max(1, int(3 * (1 - progress * 0.7)))
        sway = sway_base * progress * progress
        
        stem_x = int(cx + sway)
        stem_y = cy - (SIZE // 3) + i
        stem_z = cz
        
        # Draw stem with thickness
        for dx in range(-thickness, thickness + 1):
            for dz in range(-thickness, thickness + 1):
                if dx*dx + dz*dz <= thickness*thickness:
                    add_voxel(volume, stem_x + dx, stem_y, stem_z + dz, stem_color)

def generate_frond(volume, start_x, start_y, start_z, angle, height_offset, t):
    # Color gradient from dark to bright green
    base_green = (34, 87, 34)
    tip_green = (50, 205, 50)
    
    frond_length = MAX_FROND_LENGTH + int(5 * np.sin(height_offset * 0.3))
    
    for i in range(frond_length):
        progress = i / frond_length
        
        # Main frond curve
        curve = np.sin(progress * np.pi) * 0.3
        wind_sway = np.sin(t * 1.2 + height_offset * 0.1 + angle) * progress * 3
        
        # Position along frond
        fx = int(start_x + np.cos(angle) * i * 1.5 + wind_sway)
        fy = int(start_y + curve * 8 + np.sin(t * 0.7 + i * 0.1) * progress * 2)
        fz = int(start_z + np.sin(angle) * i * 1.5)
        
        # Color interpolation
        color = tuple(int(base_green[j] + (tip_green[j] - base_green[j]) * progress) for j in range(3))
        
        # Main frond stem
        add_voxel(volume, fx, fy, fz, color)
        
        # Generate leaflets along the frond
        if i % 3 == 0 and i > 2:
            leaflet_count = max(1, int(6 * (1 - progress)))
            for side in [-1, 1]:
                for j in range(leaflet_count):
                    leaflet_progress = j / max(1, leaflet_count - 1)
                    
                    # Leaflet positions
                    lx = fx + int(side * (j + 1) * np.cos(angle + np.pi/2))
                    ly = fy - j
                    lz = fz + int(side * (j + 1) * np.sin(angle + np.pi/2))
                    
                    # Leaflet color (slightly darker)
                    leaflet_color = tuple(max(0, int(c * (0.8 + leaflet_progress * 0.2))) for c in color)
                    add_voxel(volume, lx, ly, lz, leaflet_color)

def generate_fern(volume, cx, cy, cz, t):
    # Generate main stem
    generate_stem(volume, cx, cy, cz, t)
    
    # Generate fronds at different heights and angles
    for i in range(FROND_COUNT):
        height_progress = i / FROND_COUNT
        height_offset = int(STEM_HEIGHT * height_progress * 0.8)
        
        # Spiral arrangement of fronds
        angle = (i / FROND_COUNT) * 4 * np.pi + t * 0.1
        
        # Frond starting position
        sway = np.sin(t * 0.8) * height_progress * height_progress * 1.5
        start_x = int(cx + sway)
        start_y = cy - (SIZE // 3) + height_offset + 10
        start_z = cz
        
        generate_frond(volume, start_x, start_y, start_z, angle, height_offset, t)

def add_ground_detail(volume, cx, cy, cz):
    # Add some ground/soil detail
    ground_color = (139, 115, 85)  # Sandy brown
    ground_y = cy - (SIZE // 3) - 5
    
    for dx in range(-8, 9):
        for dz in range(-8, 9):
            if dx*dx + dz*dz <= 64:  # Circular ground patch
                for dy in range(3):
                    if np.random.random() > 0.3:  # Sparse ground detail
                        add_voxel(volume, cx + dx, ground_y + dy, cz + dz, ground_color)

def generate_scene(volume, t):
    generate_fern(volume, CENTER_X, CENTER_Y, CENTER_Z, t)
    if t == 0:  # Only add ground detail once
        add_ground_detail(volume, CENTER_X, CENTER_Y, CENTER_Z)

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

for frame in tqdm(range(FRAMES), desc="Generating fern"):
    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 FROND_COUNT to make the fern bushier or sparser
Modify the color gradients in base_green and tip_green for different fern varieties
Change the swaying frequency by adjusting the multipliers in the np.sin(t * ...) expressions
Add multiple ferns by calling generate_fern() with different center positions
Experiment with MAX_FROND_LENGTH to create larger or smaller fern varieties

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