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gsply

Ultra-Fast Gaussian Splatting PLY + SPZ I/O Library

Python License: MIT Documentation Tests

93M Gaussians/sec read | 57M Gaussians/sec write | Auto-optimized

Quick Start • Installation • Examples • API Reference • Performance

Quick Start

from gsply import plyread, GSData, GSTensor

# Read PLY file (auto-detects format, zero-copy)
data = plyread("model.ply")  # Functional API

# Or use object-oriented API
data = GSData.load("model.ply")  # Classmethod

# Access fields
positions = data.means    # (N, 3) xyz coordinates
colors = data.sh0         # (N, 3) RGB colors
scales = data.scales      # (N, 3) scale parameters
rotations = data.quats    # (N, 4) quaternions

# Save PLY file
data.save("output.ply")  # Uncompressed
data.save("output.ply", compressed=True)  # Compressed (71-74% smaller)

# GPU acceleration (optional)
gstensor = GSTensor.load("model.ply", device='cuda')
gstensor.save("output.compressed.ply")  # GPU compression

Performance: 93M Gaussians/sec read, 57M Gaussians/sec write (400K Gaussians in 6-7ms)

Overview

Ultra-fast Gaussian Splatting PLY and SPZ I/O for Python. Zero-copy reads, auto-optimized writes, optional GPU acceleration.

Key Features

  • Ultra-Fast: 93M Gaussians/sec read, 57M Gaussians/sec write
  • Zero-Copy: Reads use memory views for maximum performance
  • Auto-Optimized: Writes are 2.6-2.8x faster automatically
  • Format Support: Uncompressed PLY + PlayCanvas compressed (71-74% smaller) + SOG + Niantic SPZ (v1–v4)
  • GPU Ready: Optional PyTorch integration with GSTensor (11x faster transfers)
  • Python-first: NumPy + Numba core with bundled C++ acceleration in v0.4.2+ wheels
  • Object-Oriented API: data.save(), GSData.load(), gstensor.save(), GSTensor.load()
  • Format Conversion: normalize(), denormalize() with fused kernels (~8-15x faster)
  • Color Conversion: to_rgb(), to_sh() for SH ↔ RGB conversion
  • Comprehensive: 438 passing tests, 22 skipped optional-environment tests, full type hints, extensive documentation

Installation

Basic Installation

pip install gsply

Core dependencies: NumPy and Numba (automatically installed)

Current PyPI wheel status (v0.4.2+): pip install gsply installs the bundled gsply_cpp extension automatically on supported platform wheels: Linux x86_64, Windows AMD64, and macOS arm64 for CPython 3.10-3.13. The Python backend remains the default at runtime; opt into C++ with gsply.use_backend("cpp") or gsply.use_backend("auto").

Optional Features

GPU Acceleration (PyTorch):

pip install torch

Enables GSTensor, plyread_gpu(), plywrite_gpu(), read_spz_gpu(), and GPU-accelerated format conversions.

SOG Format Support:

pip install gsply[sogs]

Enables sogread() for reading SOG (Spatially Ordered Gaussians) format files.

C++ acceleration backend (bundled wheels):

pip install gsply installs the gsply_cpp backend automatically from the published v0.4.2+ platform wheels on supported platforms. No gsply[cpp] extra and no separate gsply-cpp package are needed.

pip install gsply

If pip uses the sdist, or if the platform has no matching wheel, the install can remain Python-only by default. To build the extension locally from the repository root, opt in explicitly:

pip install . -Cwheel.cmake=true -Ccmake.define.GSPLY_BUILD_CPP=ON

Then opt in at runtime (the Python backend remains the default):

import gsply
gsply.use_backend("cpp")        # or "auto" (use C++ if importable), or "python"
# equivalently: set the env var GSPLY_BACKEND=cpp before importing gsply
print(gsply.active_backend())   # -> "cpp" when gsply_cpp is installed

data = gsply.read_spz("scene.spz")      # routed through C++ when enabled
gsply.write_spz("out.spz", data, version=4)

When enabled, plyread/plywrite/read_spz/write_spz use gsply_cpp where it applies and fall back to pure Python otherwise (e.g. compressed PLY). Reads are float32-ULP-identical to the Python path; writes may differ by <=1 LSB per quantized value and use a different compressor (decoded data matches; compressed bytes differ).

For non-Python C++ applications, use the standalone CMake target in cpp/: add_subdirectory(path/to/gsply/cpp) then link gsplycpp::core and include gsplycpp.hpp. See cpp/README.md.

Full Installation:

pip install "gsply[sogs,spz]" torch  # GPU + SOG + SPZ v4 support

Development:

git clone https://github.com/OpsiClear/gsply.git
cd gsply
pip install -e .[dev]  # Includes pytest, ruff, mypy

Examples

Basic I/O

from gsply import plyread, plywrite, GSData

# Read PLY file
data = plyread("model.ply")
print(f"Loaded {len(data)} Gaussians")

# Object-oriented API
data = GSData.load("model.ply")  # Auto-detects format
data.save("output.ply")  # Uncompressed
data.save("output.ply", compressed=True)  # Compressed

# Unpack to individual arrays
means, scales, quats, opacities, sh0, shN = data.unpack()

# Write with individual arrays
plywrite("output.ply", means, scales, quats, opacities, sh0, shN)

Format Conversion

from gsply import GSData
import numpy as np

# Load PLY file (log-scales, logit-opacities)
data = GSData.load("scene.ply")

# Convert to linear format for easier manipulation
data.denormalize()  # Uses fused kernel (~8-15x faster)

# Modify in linear space
data.opacities = np.clip(data.opacities * 1.2, 0, 1)
data.scales *= 1.1

# Convert back to PLY format before saving
data.normalize()  # Uses fused kernel (~8-15x faster)
data.save("modified.ply")

GPU Acceleration

from gsply import GSTensor, plyread_gpu, plywrite_gpu, read_spz_gpu

# Direct GPU I/O (4-5x faster than CPU decompress + GPU transfer)
gstensor = plyread_gpu("model.compressed.ply", device='cuda')

# Direct SPZ decode to tensors. Container decompression happens on CPU, then
# packed SPZ sections are uploaded once and unpacked with PyTorch ops.
spz_tensor = read_spz_gpu("model.spz", device='cuda')

# Or convert from CPU
data = GSData.load("model.ply")
gstensor = GSTensor.from_gsdata(data, device='cuda')

# Access GPU tensors
positions_gpu = gstensor.means  # torch.Tensor on GPU
colors_gpu = gstensor.sh0        # torch.Tensor on GPU

# Filter on GPU
high_opacity = gstensor[gstensor.opacities > 0.5]

# GPU format conversion
gstensor.denormalize()  # GPU-accelerated

# Write back (GPU compression)
gstensor.save("output.compressed.ply")  # GPU compression by default

Creating from External Data

from gsply import GSData, GSTensor
import numpy as np
import torch

# Create GSData from arrays with format preset
data = GSData.from_arrays(
    means=np.random.randn(1000, 3),
    scales=np.random.rand(1000, 3),
    quats=np.random.randn(1000, 4),
    opacities=np.random.rand(1000),
    sh0=np.random.randn(1000, 3),
    format="linear"  # or "auto", "ply", "rasterizer"
)

# Create GSTensor from tensors
gstensor = GSTensor.from_arrays(
    means=torch.randn(1000, 3),
    scales=torch.rand(1000, 3),
    quats=torch.randn(1000, 4),
    opacities=torch.rand(1000),
    sh0=torch.randn(1000, 3),
    format="linear",
    device="cuda"
)

Data Manipulation

from gsply import GSData

# Slicing and indexing
subset = data[100:200]                    # Slice
first = data[0]                          # Single Gaussian
filtered = data[data.opacities > 0.5]    # Boolean mask

# Concatenation
combined = data1 + data2                 # Pairwise (1.9x faster)
merged = GSData.concatenate([data1, data2, data3])  # Bulk (6.15x faster)

# Optimize for faster operations
data = data.make_contiguous()            # 2-45x speedup for operations

# Copy and modify
bright = data.copy()
bright.sh0 *= 1.5  # Make brighter

In-Memory Compression

from gsply import compress_to_bytes, decompress_from_bytes

# Compress for network transfer or storage
compressed_bytes = compress_to_bytes(data)

# Decompress from bytes
data_restored = decompress_from_bytes(compressed_bytes)

SPZ Format (Niantic)

from gsply import read_spz, read_spz_gpu, write_spz

# Read any SPZ — the container is auto-detected (legacy gzip v1/v2/v3 or NGSP v4
# zstd). Returns a GSData in PLY format, same API as plyread().
data = read_spz("scene.spz")

# PyTorch path: returns GSTensor on the requested device.
# This avoids materializing the decoded float arrays on CPU before upload.
gstensor = read_spz_gpu("scene.spz", device="cuda")

# Write v3 (gzip, smallest-three quats) — the default
write_spz("out.spz", data)

# Write v4 (NGSP container, per-attribute zstd) — Niantic's modern format, ~3% smaller
write_spz("out_v4.spz", data, version=4)               # zstd_level=12 (default)
write_spz("fast.spz",   data, version=4, zstd_level=9) # ~2.3x faster write, +0.8% size

v4 needs the zstd extra (pip install gsply[spz]); v1–v3 work without it (large v3 writes use a core parallel gzip fallback when isal is not present; isal remains preferred when installed).

SOG Format (Optional)

from gsply import sogread

# Read SOG file - returns GSData (same API as plyread)
data = sogread("model.sog")
positions = data.means
colors = data.sh0

# Read unbundled splat-transform output
data = sogread("model/meta.json")

# Read from bytes (in-memory, no disk I/O)
with open("model.sog", "rb") as f:
    sog_bytes = f.read()
data = sogread(sog_bytes)  # Fully in-memory extraction

# SOG returns PLY-format values: log-scales and logit-opacities.
linear = data.denormalize(inplace=False)

Performance

Benchmark Summary

Uncompressed Format (400K Gaussians, SH0):

  • Read: 5.7ms (70M Gaussians/sec)
  • Write: 19.3ms (21M Gaussians/sec)

Compressed Format (400K Gaussians, SH0):

  • Read: 8.5ms (47M Gaussians/sec)
  • Write: 15.0ms (27M Gaussians/sec)
  • Size reduction: 71-74%

Peak Performance:

  • Read: 78M Gaussians/sec (1M Gaussians, SH0, uncompressed)
  • Write: 29M Gaussians/sec (100K Gaussians, SH0, compressed)

GPU Transfer (400K Gaussians, RTX 3090 Ti):

  • With _base optimization: 1.99ms (11x faster, single tensor transfer)
  • Without _base: 22.78ms (CPU copy + transfer)

Format Conversion (Fused Kernels):

  • normalize() / denormalize(): ~8-15x faster with parallel Numba kernels
  • Single-pass processing reduces memory overhead

See detailed performance benchmarks for more information.

Format Support

Uncompressed PLY

Standard binary little-endian PLY format:

SH Degree Properties Description
0 14 xyz, f_dc(3), opacity, scales(3), quats(4)
1 23 + 9 f_rest coefficients
2 38 + 24 f_rest coefficients
3 59 + 45 f_rest coefficients

Compressed PLY (PlayCanvas)

Chunk-based quantized format:

  • Automatically saves as .compressed.ply when compressed=True
  • Compression ratio: 71-74% size reduction
  • Compatible with PlayCanvas, SuperSplat, other WebGL viewers
  • Parallel compression/decompression with Numba JIT

SOG Format (Spatially Ordered Gaussians) - Optional

WebP-based texture format for web deployment:

  • Requires gsply[sogs] installation
  • Uses WebP images for efficient storage
  • Codebook-based compression for scales and colors
  • Compatible with PlayCanvas splat-transform
  • Supports current version: 2 SOG and legacy V1 assets without a version field
  • Supports .sog ZIP bundles, folders, direct meta.json paths, and ZIP bytes
  • Returns GSData container (same API as plyread())
  • Returns PLY-format log-scales and logit-opacities; call denormalize() for linear scales/opacities
  • Invalid quaternion tags fall back to the canonical wxyz identity quaternion [1, 0, 0, 0], matching splat-transform
  • In-memory ZIP extraction: can read bundled SOG directly from bytes

SPZ (Niantic) - Optional

Niantic SPZ, read + write, both containers:

  • Legacy gzip (v1/v2/v3): one gzip stream; v3 uses smallest-three quaternions
  • NGSP v4: per-attribute zstd streams behind a 32-byte header + table of contents — Niantic's current format, ~3% smaller than gzip
  • Container is auto-detected on read; write_spz(..., version=3) (default, gzip) or version=4 (NGSP/zstd, zstd_level tunable). read_spz/write_spz use the PLY-format GSData API, round-trip with the Niantic reference both directions.
  • Requires gsply[spz] for v4 (zstd); v1–v3 work with the core package. Large v3 writes use a parallel single-member gzip fallback unless isal is present.

API Reference

Complete API documentation: docs/API_REFERENCE.md

Core I/O

  • plyread(file_path) - Read PLY files (auto-detects format)
  • plywrite(file_path, ...) - Write PLY files
  • read_spz(file_path) - Read Niantic SPZ (gzip v1/v2/v3 or NGSP v4 zstd)
  • read_spz_gpu(file_path, device="cuda") - Read SPZ into GSTensor with tensor decode
  • write_spz(file_path, data, *, version=3, ...) - Write SPZ (v3 gzip / v4 zstd)
  • detect_format(file_path) - Detect format and SH degree
  • sogread(file_path | meta_json_path | bytes) - Read SOG files (optional)

GSData Container

  • GSData.load(file_path) - Load from PLY (classmethod)
  • data.save(file_path, compressed=False) - Save to PLY
  • GSData.from_arrays(...) - Create from arrays with format preset
  • GSData.from_dict(...) - Create from dictionary with format preset
  • data.normalize() / data.denormalize() - Format conversion (fused kernels, ~8-15x faster)
  • data.to_rgb() / data.to_sh() - Color conversion
  • Format query: is_scales_ply, is_scales_linear, is_opacities_ply, is_opacities_linear, is_sh0_sh, is_sh0_rgb, is_sh_order_0/1/2/3
  • data[index] - Indexing and slicing
  • data.unpack() - Unpack to tuple
  • data.copy() - Deep copy

Compression APIs

  • compress_to_bytes(data) - Compress to bytes
  • compress_to_arrays(data) - Compress to arrays
  • decompress_from_bytes(bytes) - Decompress from bytes

Utility Functions

  • sh2rgb(sh) / rgb2sh(rgb) - Color conversion
  • logit(x) / sigmoid(x) - Optimized CPU functions
  • apply_pre_activations(data, ...) - Fused activation kernel (~8-15x faster)
  • apply_pre_deactivations(data, ...) - Fused deactivation kernel (~8-15x faster)
  • SH_C0 - Normalization constant

GPU Support (PyTorch)

  • GSTensor.load(file_path, device='cuda') - Load from PLY (classmethod)
  • gstensor.save(file_path, compressed=True) - Save with GPU compression
  • GSTensor.from_arrays(...) - Create from tensors with format preset
  • GSTensor.from_gsdata(data, device='cuda') - Convert to GPU
  • gstensor.to_gsdata() - Convert to CPU
  • gstensor.normalize() / gstensor.denormalize() - GPU format conversion
  • gstensor.to_rgb() / gstensor.to_sh() - GPU color conversion
  • Format query: is_scales_ply, is_scales_linear, is_opacities_ply, is_opacities_linear, is_sh0_sh, is_sh0_rgb, is_sh_order_0/1/2/3
  • Device management: .to(), .cpu(), .cuda()
  • Precision: .half(), .float(), .double()

What's New

v0.4.6 - SPZ v4 Write Scheduling

  • Faster SPZ v4 writes: Python and C++ writers now use adaptive zstd scheduling for NGSP attribute streams, avoiding worker oversubscription on typical SH3 assets while keeping large-stream threading available.
  • Compatibility preserved: SPZ quantization, zstd level, fractional bits, stream order, and decoded parity are unchanged.

v0.4.5 - C++ Backend Performance Routing

  • C++ PLY parity without slow paths: C++ reads now preserve an aligned canonical _base row buffer, so read-backed writes keep the zero-copy path.
  • Smarter backend dispatch: gsply.use_backend("cpp") now routes PLY writes through C++ only for generated higher-order SH data where it wins; SH0 and read-backed _base writes stay on the faster Python paths.
  • SPZ routing tuned: SPZ v4 reads use the Python zstd path when available, while C++ remains the fallback for environments without zstandard.

v0.4.4 - SOG Parity and Normalization Correctness

  • SOG parity: sogread() now follows the current PlayCanvas splat-transform reader for version: 2, legacy V1 assets, direct meta.json paths, and unknown-version errors.
  • Normalization correctness: SOG data remains in PLY-format log-scales and logit-opacities, and activated exp/sigmoid values match splat-transform round trips.
  • Quaternion fallback: Invalid SOG tags and zero-norm activation fallback now use canonical wxyz identity [1, 0, 0, 0].

v0.4.3 - SPZ v3 Python Write Performance

  • Faster pure-Python SPZ v3 writes: Large write_spz(..., version=3) payloads now use a parallel single-member gzip fallback when isal is not installed.
  • Compatibility preserved: The optimized path still emits one strict gzip member and round-trips through the same SPZ reader and Niantic-compatible payload format.

v0.4.2 - Bundled Platform Wheels

  • Bundled C++ wheels: pip install gsply installs gsply_cpp automatically on supported CPython 3.10-3.13 platform wheels.
  • No separate C++ extra: No gsply[cpp] extra or separate gsply-cpp package is needed.

v0.2.11 - GPU Compression Optimization

  • torch.compile() Auto-Optimization: GPU compression now uses torch.compile() when available
    • ~25% faster GPU compression (5.0ms → 4.0ms for 365K Gaussians)
    • Automatic fallback to eager mode if compilation fails
    • Zero configuration required - works transparently
  • GPU Rounding Fix: Fixed quaternion quantization to match CPU behavior exactly
  • Platform Support: Triton backend on Linux (standard), Windows (requires triton-windows package)

v0.2.9 - Protocol Interfaces & Performance Optimization

  • Protocol Interfaces: Type-safe interfaces for format management
    • FormatAware - Protocol for objects that track format state
    • Normalizable - Protocol for objects that support format conversion
    • GaussianContainer - Protocol for objects containing Gaussian splat data
    • Enables structural typing across GSData and GSTensor
  • Format Management API: Advanced format control methods
    • format_state property - Returns current format as immutable dictionary
    • copy_format_from(other) - Copy format state from another object
    • with_format(**kwargs) - Create shallow copy with modified format
  • Performance Optimizations: Improved efficiency for common operations
    • Removed auto-consolidate overhead in plywrite() - users can call make_contiguous() manually when needed
    • In-place format conversion now default (inplace=True) - reduces memory allocations
    • Better performance for already-contiguous data

v0.2.8 - Format Query Properties

  • Format Query Properties: Convenient boolean properties to check current data format
    • is_scales_ply, is_scales_linear - Check scale format
    • is_opacities_ply, is_opacities_linear - Check opacity format
    • is_sh0_sh, is_sh0_rgb - Check color format
    • is_sh_order_0/1/2/3 - Check SH degree
    • Available on both GSData and GSTensor

v0.2.7 - Fused Activation Kernels & Performance Optimization

  • Fused Activation Kernels: Ultra-fast format conversion with parallel Numba kernels
    • apply_pre_activations() - Fused kernel for activating scales, opacities, and quaternions (~8-15x faster)
    • apply_pre_deactivations() - Fused kernel for deactivating scales and opacities (~8-15x faster)
    • normalize() and denormalize() now use optimized fused kernels internally
    • Single-pass processing reduces memory overhead and improves cache locality

v0.2.6 - Format Safety & Auto-detection

  • Convenience Factory Methods: GSData.from_arrays(), GSData.from_dict(), GSTensor.from_arrays(), GSTensor.from_dict()
  • Auto-Format Detection: Smart heuristics automatically detect PLY vs Linear format
  • Format Safety: Strict validation prevents mixing incompatible formats
  • Format Helpers: create_ply_format(), create_rasterizer_format()

v0.2.5 - SOG Format Support & API Improvements

  • SOG Format Support: sogread() - Read SOG (Spatially Ordered Gaussians) format files
  • Object-Oriented I/O API: data.save(), GSData.load(), gstensor.save(), GSTensor.load()
  • Format Conversion API: normalize(), denormalize() for linear ↔ PLY format conversion
  • Color Conversion API: to_rgb(), to_sh() for SH ↔ RGB conversion

Full Changelog • API Reference

Development

Setup

# Clone repository
git clone https://github.com/OpsiClear/gsply.git
cd gsply

# Install in development mode
pip install -e .[dev]

# Run tests
pytest tests/ -v

# Run with coverage
pytest tests/ -v --cov=gsply --cov-report=html

Project Structure

gsply/
├── src/gsply/          # Source code
│   ├── __init__.py     # Public API exports and lazy optional imports
│   ├── _backend.py     # gsply_cpp backend selection
│   ├── gsdata.py       # GSData dataclass
│   ├── reader.py       # PLY reading
│   ├── writer.py       # PLY writing
│   ├── spz.py          # Niantic SPZ reading/writing
│   ├── sog_reader.py   # SOG reading
│   ├── formats.py      # Format detection
│   ├── utils.py        # Utility functions (fused kernels)
│   └── torch/          # PyTorch integration
│       ├── gstensor.py # GSTensor GPU dataclass
│       ├── compression.py
│       ├── spz.py      # SPZ tensor decode
│       └── io.py       # GPU I/O
├── cpp/                # Bundled C++ acceleration backend source
├── tests/              # Unit tests (460 collected)
├── benchmarks/         # Performance benchmarks
├── docs/               # Documentation
└── pyproject.toml      # Package configuration

Testing

gsply has comprehensive test coverage with 438 passed, 22 skipped, 460 collected in the latest local verification:

# Run all tests
pytest tests/ -v

# Run PyTorch tests (requires torch)
pytest tests/ -v -k "torch or gstensor"

# Run with coverage
pytest tests/ -v --cov=gsply --cov-report=html

Benchmarking

# Install benchmark dependencies
pip install -e .[benchmark]

# Run benchmark
python benchmarks/benchmark.py

Documentation

Contributing

Contributions are welcome! Please see docs/CONTRIBUTING.md for guidelines.

Quick start:

  1. Fork the repository
  2. Create a feature branch
  3. Make your changes with tests
  4. Run tests: pytest tests/ -v
  5. Submit a pull request

License

MIT License - see LICENSE file for details.

Citation

If you use gsply in your research, please cite:

@software{gsply2024,
  author = {OpsiClear},
  title = {gsply: Ultra-Fast Gaussian Splatting PLY I/O},
  year = {2024},
  url = {https://github.com/OpsiClear/gsply}
}

Related Projects

  • gsplat: CUDA-accelerated Gaussian Splatting rasterizer
  • nerfstudio: NeRF training framework with Gaussian Splatting support
  • PlayCanvas SuperSplat: Web-based Gaussian Splatting viewer
  • 3D Gaussian Splatting: Original paper and implementation

Made with Python and numpy

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Very fast python loader for gaussian splatting ply files.

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