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Gaussian Splatting

3D Gaussian Splatting Model Editing Guide

1. Introduction​

1.1 What is 3D Gaussian Splatting?​

3D Gaussian Splatting (3DGS) is a novel scene representation and rendering technology. It uses millions of oriented 3D Gaussian functions to represent a scene. Each Gaussian has position, shape (defined by covariance matrix or equivalent scale/rotation parameters), color (often using spherical harmonics for view-dependent effects), and opacity.

3DGS enables high-fidelity real-time rendering of complex scenes and excels in inverse rendering (reconstructing 3D scenes from images).

1.2 3DGS PLY File Format​

3DGS models are typically stored as .ply files. Unlike traditional mesh .ply files, 3DGS .ply files contain specific properties for each Gaussian function, such as position, color coefficients, opacity, scale, and rotation.

2. gsply_edit.py Script Introduction​

This repository provides a Python script for editing 3DGS models: scripts/gsply_edit.py. It allows users to perform translation, rotation, and scaling operations on 3DGS models.

Core functions:

  • Geometric transformation: modify the position of each Gaussian
  • Orientation adjustment: rotate each Gaussian
  • Scale adjustment: resize each Gaussian
  • Spherical harmonics (SH) rotation: automatically update SH coefficients for consistent view-dependent appearance

3. Dependencies​

Required Python libraries:

  • numpy
  • scipy
  • torch
  • einops
  • e3nn
  • tqdm

Install with:

pip install numpy scipy torch einops e3nn tqdm

4. Key Concepts​

4.1 Transformations​

Supported operations:

  • Translation (X, Y, Z)
  • Rotation (quaternion)
  • Scaling

4.2 Transformation Order​

When specifying translation, rotation, and scaling together, the script applies them in the following order:

  1. Rotation
  2. Translation
  3. Scaling

4.3 Spherical Harmonics (SH)​

SH are used to represent the view-dependent color of each Gaussian. When a Gaussian is rotated, its SH coefficients are also rotated to maintain correct appearance.

4.4 Gaussian Parameters​

Each Gaussian is defined by:

  • Position (x, y, z)
  • Rotation (rot_0, rot_1, rot_2, rot_3)
  • Scale (scale_0, scale_1, scale_2)
  • Opacity

5. Script Usage​

Command line format:

python scripts/gsply_edit.py <input_file> [options]

Options include:

  • -o, --output_file: Output file path
  • -t, --transform x y z: Translation vector
  • -r, --rotation x y z w: Quaternion rotation
  • -s, --scale S: Uniform scaling factor

6. Usage Examples​

Translate:

python scripts/gsply_edit.py data/scene.ply -o data/scene_translated.ply -t 0.5 0.0 -0.2

Rotate:

python scripts/gsply_edit.py data/scene.ply -o data/scene_rotated.ply -r 0.0 0.0 0.38268343 0.92387953

Scale:

python scripts/gsply_edit.py data/scene.ply -o data/scene_scaled.ply -s 2.0

Combined transformation:

python scripts/gsply_edit.py data/000000.ply -o data/000000_transpose.ply -t 0.3 0.4 -0.5 -r 0. 0. 0.38268343 0.92387953 -s 1.5

7. Online Editing Tools​

In addition to the script, you can use online tools for visual editing: 3dgs Online Editor (SuperSplat Editor) Features include:

  1. Translation
  2. Rotation
  3. Scaling
  4. Multi-selection
  5. Deletion
  6. Switching rendering modes

By combining precise script-based control and online visual editing, you can efficiently process and optimize 3D Gaussian Splatting models for high-quality assets in DISCOVERSE simulation environments.