Growing Bush - 3D Voxel Animation Tutorial

This guide walks you through how to generate a looping 3D voxel animation of a growing bush using SpatialStudio. The script creates a realistic bush that grows, sways gently in the wind, and develops seasonal foliage changes 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 growing bush with:
- A sturdy brown trunk base
- Branching woody stems
- Lush green foliage that grows over time
- Natural swaying motion in the wind
Animates the growth and movement for 10 seconds at 30 FPS
Outputs the file bush.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).
Bush structure The bush is built from the ground up with a trunk, main branches, and smaller twigs using recursive branching.
Foliage growth Leaves appear and grow around branch endpoints, with density increasing over time using the animation parameter.
Wind simulation Branches and leaves sway using sine waves with different frequencies to create natural movement.
Seasonal variation Leaf colors subtly shift throughout the animation cycle, simulating seasonal changes.
Animation loop A normalized time variable t cycles from 0 → 2π, ensuring smooth looping growth and 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 bush.py and run:

python bush.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/bush.splv"

# Bush settings
TRUNK_HEIGHT = 15
BRANCH_COUNT = 8
MAX_BRANCH_DEPTH = 3
FOLIAGE_DENSITY = 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_trunk(volume, cx, cy, cz, height, t):
    trunk_color = (101, 67, 33)  # Brown
    wind_sway = np.sin(t * 0.8) * 2
    
    for y in range(height):
        growth_factor = min(1.0, (t / (2*np.pi)) * 2.0)  # Grow over first half
        if y < height * growth_factor:
            thickness = max(1, 3 - y // 5)  # Trunk gets thinner as it goes up
            sway_x = int(wind_sway * (y / height))
            
            for dx in range(-thickness, thickness+1):
                for dz in range(-thickness, thickness+1):
                    if dx*dx + dz*dz <= thickness*thickness:
                        bark_texture = int(np.sin(y*0.3 + dx*0.5 + dz*0.5) * 20)
                        bark_color = tuple(max(0, c + bark_texture) for c in trunk_color)
                        add_voxel(volume, cx+dx+sway_x, cy+y, cz+dz, bark_color)

def generate_branch(volume, start_x, start_y, start_z, length, angle_h, angle_v, depth, t, growth_time):
    if depth <= 0 or length < 3:
        return
    
    branch_color = (139, 90, 43)  # Lighter brown for branches
    wind_offset = np.sin(t * 1.2 + angle_h) * (4 - depth)
    
    # Calculate branch direction
    dx = np.cos(angle_h) * np.cos(angle_v)
    dy = np.sin(angle_v)
    dz = np.sin(angle_h) * np.cos(angle_v)
    
    branch_points = []
    
    # Draw branch segments
    for i in range(int(length)):
        progress = i / length
        if progress < growth_time:  # Only draw if grown enough
            x = int(start_x + dx * i + wind_offset * progress)
            y = int(start_y + dy * i)
            z = int(start_z + dz * i + np.sin(t * 0.9 + i*0.1) * progress)
            
            thickness = max(1, int(2 * (1 - progress)))
            for dt in range(-thickness, thickness+1):
                for dk in range(-thickness, thickness+1):
                    if dt*dt + dk*dk <= thickness*thickness:
                        add_voxel(volume, x+dt, y, z+dk, branch_color)
            
            branch_points.append((x, y, z))
    
    # Generate sub-branches
    if len(branch_points) > length // 2 and growth_time > 0.5:
        end_x, end_y, end_z = branch_points[-1]
        
        # Create 2-3 smaller branches
        for i in range(2):
            new_angle_h = angle_h + (i - 0.5) * 1.2
            new_angle_v = angle_v + np.random.uniform(-0.3, 0.3)
            new_length = length * 0.7
            sub_growth = max(0, growth_time - 0.3)
            
            generate_branch(volume, end_x, end_y, end_z, new_length, 
                          new_angle_h, new_angle_v, depth-1, t, sub_growth)

def generate_foliage(volume, cx, cy, cz, t, growth_time):
    if growth_time < 0.4:  # Leaves appear later
        return
    
    leaf_growth = (growth_time - 0.4) / 0.6
    seasonal_shift = np.sin(t * 0.5) * 0.3
    
    # Base green with seasonal variation
    base_green = (34, 139, 34)
    seasonal_green = tuple(int(c * (1 + seasonal_shift)) for c in base_green)
    
    foliage_size = int(FOLIAGE_DENSITY * leaf_growth)
    
    for i in range(foliage_size):
        # Random foliage placement around the center
        angle = (i / foliage_size) * 4*np.pi
        radius = 3 + np.random.uniform(0, 4)
        height_offset = np.random.uniform(-2, 8)
        
        leaf_x = int(cx + radius * np.cos(angle + t*0.3))
        leaf_y = int(cy + height_offset)
        leaf_z = int(cz + radius * np.sin(angle + t*0.2))
        
        # Add some wind movement to leaves
        wind_x = int(np.sin(t * 1.5 + i*0.1) * 2)
        wind_z = int(np.cos(t * 1.3 + i*0.15) * 2)
        
        # Create small leaf clusters
        for dx in range(-1, 2):
            for dy in range(-1, 2):
                for dz in range(-1, 2):
                    if abs(dx) + abs(dy) + abs(dz) <= 2:  # Diamond shape
                        leaf_color_var = np.random.randint(-20, 20, 3)
                        final_color = tuple(max(0, min(255, seasonal_green[i] + leaf_color_var[i])) 
                                          for i in range(3))
                        add_voxel(volume, leaf_x+dx+wind_x, leaf_y+dy, 
                                leaf_z+dz+wind_z, final_color)

def generate_main_branches(volume, cx, cy, cz, t, growth_time):
    for i in range(BRANCH_COUNT):
        if growth_time > i * 0.1:  # Stagger branch growth
            angle = (i / BRANCH_COUNT) * 2*np.pi
            start_height = TRUNK_HEIGHT - 5 + i * 2
            branch_length = 8 + np.random.uniform(0, 4)
            
            # Vary branch angles for natural look
            angle_v = np.random.uniform(0.1, 0.4)  # Upward angle
            branch_growth = max(0, growth_time - i * 0.1)
            
            generate_branch(volume, cx, cy + start_height, cz, 
                          branch_length, angle, angle_v, MAX_BRANCH_DEPTH, 
                          t, branch_growth)

def generate_scene(volume, t):
    growth_progress = (t / (2*np.pi))  # 0 to 1 over full cycle
    
    # Generate bush components
    generate_trunk(volume, CENTER_X, CENTER_Y - 20, CENTER_Z, TRUNK_HEIGHT, t)
    generate_main_branches(volume, CENTER_X, CENTER_Y - 20, CENTER_Z, t, growth_progress)
    
    # Add foliage to branch endpoints
    for i in range(BRANCH_COUNT):
        angle = (i / BRANCH_COUNT) * 2*np.pi
        foliage_x = CENTER_X + int(8 * np.cos(angle))
        foliage_y = CENTER_Y - 5 + i
        foliage_z = CENTER_Z + int(8 * np.sin(angle))
        
        generate_foliage(volume, foliage_x, foliage_y, foliage_z, t, growth_progress)

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

# Generate animation frames
for frame in tqdm(range(FRAMES), desc="Growing bush"):
    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 BRANCH_COUNT to create bushier or sparser growth.
Modify FOLIAGE_DENSITY for more or less leafy appearance.
Change the seasonal color variations in generate_foliage() for autumn effects.
Experiment with MAX_BRANCH_DEPTH for more complex branching patterns.
Add flowers by creating small colorful voxel clusters on branches.

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