3D Voxel Animation: Cactus

This guide walks you through how to generate a looping 3D voxel animation of cacti using SpatialStudio. The script creates a desert scene with various cacti that sway gently and bloom with colorful flowers 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 6 different cacti, each with:
- Segmented cylindrical stems
- Branching arms at various heights
- Colorful blooming flowers on top
- Subtle swaying motion in the wind
Adds a sandy desert floor for realism
Animates them swaying naturally for 10 seconds at 30 FPS
Outputs the file cactus.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).
Cactus stems Cacti are drawn as vertical cylinders with segmented texture patterns for realistic ridged appearance.
Branching arms Each cactus gets 1-3 horizontal arms that extend outward at different heights and angles.
Blooming flowers Colorful voxel clusters are placed on top of stems and arms to simulate desert flowers.
Desert floor Sandy-colored voxels create a textured ground surface with subtle height variations.
Wind animation A normalized time variable t creates gentle swaying motion that loops smoothly.
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 cactus.py and run:

python cactus.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/cactus.splv"

# Cactus settings
CACTUS_COUNT = 6
BASE_HEIGHT = 25
ARM_LENGTH = 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_desert_floor(volume):
    sand_color = (194, 178, 128)
    for x in range(SIZE):
        for z in range(SIZE):
            # Create subtle height variation
            height_noise = int(np.sin(x*0.1) * np.cos(z*0.1) * 3)
            floor_height = 15 + height_noise
            for y in range(floor_height):
                # Add texture variation to sand
                brightness = 0.9 + 0.2 * np.sin(x*0.3 + z*0.2 + y*0.5)
                final_color = tuple(int(c * brightness) for c in sand_color)
                add_voxel(volume, x, y, z, final_color)

def generate_cactus_stem(volume, cx, cy, cz, height, t, sway_factor=1.0):
    stem_color = (34, 139, 34)  # Forest green
    ridge_color = (28, 120, 28)  # Darker green for ridges
    
    for y in range(height):
        # Calculate sway offset
        sway_x = int(np.sin(t * 1.2 + cy * 0.05) * (y * 0.1) * sway_factor)
        sway_z = int(np.cos(t * 0.8 + cy * 0.03) * (y * 0.08) * sway_factor)
        
        # Draw cylindrical stem with ridges
        for dx in range(-3, 4):
            for dz in range(-3, 4):
                distance = np.sqrt(dx*dx + dz*dz)
                if distance <= 3:
                    # Create vertical ridges
                    ridge = abs(dx) == 3 or abs(dz) == 3 or (abs(dx) == 2 and abs(dz) == 2)
                    color = ridge_color if ridge else stem_color
                    
                    # Add segment texture
                    if y % 8 == 0:
                        color = tuple(max(20, c - 15) for c in color)
                    
                    add_voxel(volume, cx + dx + sway_x, cy + y, cz + dz + sway_z, color)

def generate_cactus_arm(volume, cx, cy, cz, direction, length, t):
    stem_color = (34, 139, 34)
    arm_y = cy
    
    for i in range(length):
        # Calculate arm position with slight upward curve
        curve = int(np.sin(i * 0.2) * 2)
        sway = int(np.sin(t * 1.5 + i * 0.1) * 0.5)
        
        if direction == 'x':
            arm_x, arm_z = cx + i, cz + sway
        else:  # direction == 'z'
            arm_x, arm_z = cx + sway, cz + i
        
        # Draw arm cylinder (smaller than main stem)
        for dx in range(-2, 3):
            for dz in range(-2, 3):
                if dx*dx + dz*dz <= 4:
                    add_voxel(volume, arm_x + dx, arm_y + curve, arm_z + dz, stem_color)

def generate_cactus_flower(volume, cx, cy, cz, color, t):
    # Animated blooming effect
    bloom_factor = 0.5 + 0.5 * np.sin(t * 2.0)
    flower_size = int(3 * bloom_factor) + 1
    
    for dx in range(-flower_size, flower_size + 1):
        for dy in range(-2, 3):
            for dz in range(-flower_size, flower_size + 1):
                distance = np.sqrt(dx*dx + dy*dy*0.5 + dz*dz)
                if distance <= flower_size:
                    # Add some sparkle effect
                    sparkle = int(np.sin(t * 5.0 + dx + dz) * 20)
                    final_color = tuple(min(255, max(0, c + sparkle)) for c in color)
                    add_voxel(volume, cx + dx, cy + dy, cz + dz, final_color)

def generate_single_cactus(volume, base_x, base_z, cactus_id, t):
    flower_colors = [
        (255, 100, 150),  # Pink
        (255, 200, 50),   # Yellow
        (255, 80, 80),    # Red
        (150, 100, 255),  # Purple
        (100, 255, 150),  # Light green
        (255, 150, 100),  # Orange
    ]
    
    # Vary cactus properties based on ID
    height = BASE_HEIGHT + int(15 * np.sin(cactus_id * 1.3))
    base_y = 15
    
    # Generate main stem
    generate_cactus_stem(volume, base_x, base_y, base_z, height, t)
    
    # Add arms (not all cacti have arms)
    if cactus_id % 2 == 0:  # Even numbered cacti get arms
        arm_height = height // 2 + int(5 * np.cos(cactus_id))
        arm_y = base_y + arm_height
        
        # Add 1-2 arms
        if cactus_id % 4 == 0:  # Some get two arms
            generate_cactus_arm(volume, base_x, arm_y, base_z, 'x', ARM_LENGTH, t)
            generate_cactus_arm(volume, base_x, arm_y - 8, base_z, 'z', ARM_LENGTH - 3, t)
            # Flowers on arms
            generate_cactus_flower(volume, base_x + ARM_LENGTH, arm_y + 2, base_z, 
                                 flower_colors[(cactus_id + 1) % len(flower_colors)], t)
            generate_cactus_flower(volume, base_x, arm_y - 6, base_z + ARM_LENGTH - 3, 
                                 flower_colors[(cactus_id + 2) % len(flower_colors)], t)
        else:
            generate_cactus_arm(volume, base_x, arm_y, base_z, 'x', ARM_LENGTH, t)
            # Flower on arm
            generate_cactus_flower(volume, base_x + ARM_LENGTH, arm_y + 2, base_z, 
                                 flower_colors[(cactus_id + 1) % len(flower_colors)], t)
    
    # Main flower on top
    flower_color = flower_colors[cactus_id % len(flower_colors)]
    generate_cactus_flower(volume, base_x, base_y + height + 2, base_z, flower_color, t)

def generate_cactus_garden(volume, t):
    # Position cacti in a natural scattered pattern
    positions = [
        (CENTER_X - 25, CENTER_Z - 20),
        (CENTER_X + 20, CENTER_Z - 25),
        (CENTER_X - 15, CENTER_Z + 15),
        (CENTER_X + 30, CENTER_Z + 10),
        (CENTER_X - 35, CENTER_Z + 30),
        (CENTER_X + 10, CENTER_Z - 35),
    ]
    
    for i, (x, z) in enumerate(positions):
        generate_single_cactus(volume, x, z, i, t)

def generate_scene(volume, t):
    generate_desert_floor(volume)
    generate_cactus_garden(volume, t)

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

for frame in tqdm(range(FRAMES), desc="Growing cactus garden"):
    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

Change CACTUS_COUNT to add more variety to your desert.
Edit flower_colors for different blooming patterns.
Modify BASE_HEIGHT to create taller or shorter cacti.
Add tumbleweeds by creating rolling sphere objects.
Create a day/night cycle by adjusting the flower bloom timing.
Add small desert creatures like lizards using similar voxel techniques.

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