npm package: @playcanvas/splat-transform
Description: Library and CLI tool for 3D Gaussian splat format conversion and transformation
Author: PlayCanvas
Latest version: 1.10.2

# SplatTransform - 3D Gaussian Splat Converter

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| [User Guide](https://developer.playcanvas.com/user-manual/gaussian-splatting/editing/splat-transform/) | [API Reference](https://api.playcanvas.com/splat-transform/) | [Blog](https://blog.playcanvas.com/) | [Forum](https://forum.playcanvas.com/) |

SplatTransform is an open source library and CLI tool for converting and editing Gaussian splats. It can:

📥 Read PLY, Compressed PLY, SOG, SPLAT, KSPLAT, SPZ, LCC and Voxel formats  
📤 Write PLY, Compressed PLY, SOG, GLB, CSV, HTML Viewer, LOD and Voxel formats  
📊 Generate statistical summaries for data analysis  
🔗 Merge multiple splats  
🔄 Apply transformations to input splats  
🎛️ Filter out Gaussians or spherical harmonic bands  
🔀 Reorder splats for improved spatial locality  
⚙️ Procedurally generate splats using JavaScript generators

The library is platform-agnostic and can be used in both Node.js and browser environments.

## Installation

Install or update to the latest version:

```bash
npm install -g @playcanvas/splat-transform
```

For library usage, install as a dependency:

```bash
npm install @playcanvas/splat-transform
```

## CLI Usage

```bash
splat-transform [GLOBAL] input [ACTIONS]  ...  output [ACTIONS]
```

**Key points:**
- Input files become the working set; ACTIONS are applied in order
- The last file is the output; actions after it modify the final result
- Use `null` as output to discard file output

## Supported Formats

| Format | Input | Output | Description |
| ------ | ----- | ------ | ----------- |
| `.ply` | ✅ | ✅ | Standard PLY format |
| `.sog` | ✅ | ✅ | Bundled super-compressed format (recommended) |
| `meta.json` | ✅ | ✅ | Unbundled super-compressed format (accompanied by `.webp` textures) |
| `.compressed.ply` | ✅ | ✅ | Compressed PLY format (auto-detected and decompressed on read) |
| `.lcc` | ✅ | ❌ | LCC file format (XGRIDS) |
| `.ksplat` | ✅ | ❌ | Compressed splat format (mkkellogg format) |
| `.splat` | ✅ | ❌ | Compressed splat format (antimatter15 format) |
| `.spz` | ✅ | ❌ | Compressed splat format (Niantic format) |
| `.mjs` | ✅ | ❌ | Generate a scene using an mjs script (Beta) |
| `.glb` | ❌ | ✅ | Binary glTF with [KHR_gaussian_splatting](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_gaussian_splatting) extension |
| `.csv` | ❌ | ✅ | Comma-separated values spreadsheet |
| `.html` | ❌ | ✅ | HTML viewer app (single-page or unbundled) based on SOG |
| `.voxel.json` | ✅ | ✅ | Sparse voxel octree for collision detection |

## Actions

Actions can be repeated and applied in any order:

```none
-t, --translate        <x,y,z>          Translate splats by (x, y, z)
-r, --rotate           <x,y,z>          Rotate splats by Euler angles (x, y, z) in degrees
-s, --scale            <factor>         Uniformly scale splats by factor
-H, --filter-harmonics <0|1|2|3>        Remove spherical harmonic bands > n
-N, --filter-nan                        Remove Gaussians with NaN or Inf values
-B, --filter-box       <x,y,z,X,Y,Z>    Remove Gaussians outside box (min, max corners)
-S, --filter-sphere    <x,y,z,radius>   Remove Gaussians outside sphere (center, radius)
-V, --filter-value     <name,cmp,value> Keep splats where <name> <cmp> <value>
                                          cmp ∈ {lt,lte,gt,gte,eq,neq}
-F, --decimate         <n|n%>          Simplify to n splats via progressive pairwise merging
                                          Use n% to keep a percentage of splats
-p, --params           <key=val,...>    Pass parameters to .mjs generator script
-l, --lod              <n>              Specify the level of detail of this model, n >= 0.
-m, --summary                           Print per-column statistics to stdout
-M, --morton-order                      Reorder Gaussians by Morton code (Z-order curve)
```

## Global Options

```none
-h, --help                              Show this help and exit
-v, --version                           Show version and exit
-q, --quiet                             Suppress non-error output
-w, --overwrite                         Overwrite output file if it exists
-i, --iterations       <n>              Iterations for SOG SH compression (more=better). Default: 10
-L, --list-gpus                         List all available GPU adapters and exit
-g, --gpu              <n|cpu>          Select device for SOG compression: GPU adapter index | 'cpu'
-E, --viewer-settings  <settings.json>  HTML viewer settings JSON file
-U, --unbundled                         Generate unbundled HTML viewer with separate files
-O, --lod-select       <n,n,...>        Comma-separated LOD levels to read from LCC input
-C, --lod-chunk-count  <n>              Approx number of Gaussians per LOD chunk in K. Default: 512
-X, --lod-chunk-extent <n>              Approx size of an LOD chunk in world units (m). Default: 16
-R, --voxel-resolution <n>              Voxel size in world units for .voxel.json. Default: 0.05
-A, --opacity-cutoff   <n>              Opacity threshold for solid voxels. Default: 0.1
```

> [!NOTE]
> See the [SuperSplat Viewer Settings Schema](https://github.com/playcanvas/supersplat-viewer?tab=readme-ov-file#settings-schema) for details on how to pass data to the `-E` option.

## Examples

### Basic Operations

```bash
# Simple format conversion
splat-transform input.ply output.csv

# Convert from .splat format
splat-transform input.splat output.ply

# Convert from .ksplat format
splat-transform input.ksplat output.ply

# Convert to compressed PLY
splat-transform input.ply output.compressed.ply

# Uncompress a compressed PLY back to standard PLY
# (compressed .ply is detected automatically on read)
splat-transform input.compressed.ply output.ply

# Convert to SOG bundled format
splat-transform input.ply output.sog

# Convert to SOG unbundled format
splat-transform input.ply output/meta.json

# Convert from SOG (bundled) back to PLY
splat-transform scene.sog restored.ply

# Convert from SOG (unbundled folder) back to PLY
splat-transform output/meta.json restored.ply

# Convert to standalone HTML viewer (bundled, single file)
splat-transform input.ply output.html

# Convert to unbundled HTML viewer (separate CSS, JS, and SOG files)
splat-transform -U input.ply output.html

# Convert to HTML viewer with custom settings
splat-transform -E settings.json input.ply output.html
```

### Transformations

```bash
# Scale and translate
splat-transform bunny.ply -s 0.5 -t 0,0,10 bunny_scaled.ply

# Rotate by 90 degrees around Y axis
splat-transform input.ply -r 0,90,0 output.ply

# Chain multiple transformations
splat-transform input.ply -s 2 -t 1,0,0 -r 0,0,45 output.ply
```

### Filtering

```bash
# Remove entries containing NaN and Inf
splat-transform input.ply --filter-nan output.ply

# Filter by opacity values (keep only splats with opacity > 0.5)
splat-transform input.ply -V opacity,gt,0.5 output.ply

# Strip spherical harmonic bands higher than 2
splat-transform input.ply --filter-harmonics 2 output.ply

# Simplify to 50000 splats via progressive pairwise merging
splat-transform input.ply --decimate 50000 output.ply

# Simplify to 25% of original splat count
splat-transform input.ply -F 25% output.ply
```

### Advanced Usage

```bash
# Combine multiple files with different transforms
splat-transform -w cloudA.ply -r 0,90,0 cloudB.ply -s 2 merged.compressed.ply

# Apply final transformations to combined result
splat-transform input1.ply input2.ply output.ply -t 0,0,10 -s 0.5
```

### Statistical Summary

Generate per-column statistics for data analysis or test validation:

```bash
# Print summary, then write output
splat-transform input.ply --summary output.ply

# Print summary without writing a file (discard output)
splat-transform input.ply -m null

# Print summary before and after a transform
splat-transform input.ply --summary -s 0.5 --summary output.ply
```

The summary includes min, max, median, mean, stdDev, nanCount and infCount for each column in the data.

### Generators (Beta)

Generator scripts can be used to synthesize gaussian splat data. See [gen-grid.mjs](generators/gen-grid.mjs) for an example.

```bash
splat-transform gen-grid.mjs -p width=10,height=10,scale=10,color=0.1 scenes/grid.ply -w
```

### Voxel Format

The voxel format stores sparse voxel octree data for collision detection. It consists of two files: `.voxel.json` (metadata) and `.voxel.bin` (binary octree data).

#### Writing Voxel Data

```bash
# Generate voxel collision data from a splat file
splat-transform input.ply output.voxel.json

# Generate voxel data with custom resolution (10cm voxels)
splat-transform -R 0.1 input.ply output.voxel.json

# Generate voxel data with lower opacity threshold
splat-transform -A 0.3 input.ply output.voxel.json

# Combine resolution and opacity settings
splat-transform -R 0.1 -A 0.3 input.ply output.voxel.json
```

> [!NOTE]
> The voxel resolution controls the size of individual voxels in world units. The opacity cutoff determines the threshold above which voxels are considered solid.

#### Reading Voxel Data

Voxel files can be read back and converted to other formats. The reader traverses the octree and converts leaf blocks into Gaussian splats for visualization or further processing.

```bash
# Convert voxel data back to PLY for visualization
splat-transform scene.voxel.json scene-voxels.ply

# Convert voxel data to CSV for analysis
splat-transform scene.voxel.json scene-voxels.csv
```

### Device Selection for SOG Compression

When compressing to SOG format, you can control which device (GPU or CPU) performs the compression:

```bash
# List available GPU adapters
splat-transform --list-gpus

# Let WebGPU automatically choose the best GPU (default behavior)
splat-transform input.ply output.sog

# Explicitly select a GPU adapter by index
splat-transform -g 0 input.ply output.sog  # Use first listed adapter
splat-transform -g 1 input.ply output.sog  # Use second listed adapter

# Use CPU for compression instead (much slower but always available)
splat-transform -g cpu input.ply output.sog
```

> [!NOTE]
> When `-g` is not specified, WebGPU automatically selects the best available GPU. Use `-L` to list available adapters with their indices and names. The order and availability of adapters depends on your system and GPU drivers. Use `-g <index>` to select a specific adapter, or `-g cpu` to force CPU computation.

> [!WARNING]
> CPU compression can be significantly slower than GPU compression (often 5-10x slower). Use CPU mode only if GPU drivers are unavailable or problematic.

## Getting Help

```bash
# Show version
splat-transform --version

# Show help
splat-transform --help
```

---

## Library Usage

SplatTransform exposes a programmatic API for reading, processing, and writing Gaussian splat data.

### Basic Import

```typescript
import {
    readFile,
    writeFile,
    getInputFormat,
    getOutputFormat,
    DataTable,
    processDataTable
} from '@playcanvas/splat-transform';
```

### Key Exports

| Export | Description |
| ------ | ----------- |
| `readFile` | Read splat data from various formats |
| `writeFile` | Write splat data to various formats |
| `getInputFormat` | Detect input format from filename |
| `getOutputFormat` | Detect output format from filename |
| `DataTable`, `Column` | Core data structures for splat data |
| `combine` | Merge multiple DataTables into one |
| `transform` | Apply spatial transformations |
| `processDataTable` | Apply a sequence of processing actions |
| `computeSummary` | Generate statistical summary of data |
| `sortMortonOrder` | Sort indices by Morton code for spatial locality |
| `sortByVisibility` | Sort indices by visibility score for filtering |
| `readVoxel`, `writeVoxel` | Read/write sparse voxel octree files |

### File System Abstractions

The library uses abstract file system interfaces for maximum flexibility:

**Reading:**
- `UrlReadFileSystem` - Read from URLs (browser/Node.js)
- `MemoryReadFileSystem` - Read from in-memory buffers
- `ZipReadFileSystem` - Read from ZIP archives

**Writing:**
- `MemoryFileSystem` - Write to in-memory buffers
- `ZipFileSystem` - Write to ZIP archives

### Example: Reading and Processing

```typescript
import { Vec3 } from 'playcanvas';
import {
    readFile,
    writeFile,
    getInputFormat,
    getOutputFormat,
    processDataTable,
    UrlReadFileSystem,
    MemoryFileSystem
} from '@playcanvas/splat-transform';

// Read a PLY file from URL
const fileSystem = new UrlReadFileSystem();
const inputFormat = getInputFormat('scene.ply');

const dataTables = await readFile({
    filename: 'https://example.com/scene.ply',
    inputFormat,
    options: { iterations: 10 },
    params: [],
    fileSystem
});

// Apply transformations
const processed = processDataTable(dataTables[0], [
    { kind: 'scale', value: 0.5 },
    { kind: 'translate', value: new Vec3(0, 1, 0) },
    { kind: 'filterNaN' }
]);

// Write to in-memory buffer
const memFs = new MemoryFileSystem();
const outputFormat = getOutputFormat('output.ply', {});

await writeFile({
    filename: 'output.ply',
    outputFormat,
    dataTable: processed,
    options: {}
}, memFs);

// Get the output data
const outputBuffer = memFs.files.get('output.ply');
```

### Processing Actions

The `processDataTable` function accepts an array of actions:

```typescript
type ProcessAction =
    | { kind: 'translate'; value: Vec3 }
    | { kind: 'rotate'; value: Vec3 }       // Euler angles in degrees
    | { kind: 'scale'; value: number }
    | { kind: 'filterNaN' }
    | { kind: 'filterByValue'; columnName: string; comparator: 'lt'|'lte'|'gt'|'gte'|'eq'|'neq'; value: number }
    | { kind: 'filterBands'; value: 0|1|2|3 }
    | { kind: 'filterBox'; min: Vec3; max: Vec3 }
    | { kind: 'filterSphere'; center: Vec3; radius: number }
    | { kind: 'decimate'; count: number | null; percent: number | null }
    | { kind: 'lod'; value: number }
    | { kind: 'summary' }
    | { kind: 'mortonOrder' };
```

### Custom Logging

Configure the logger for your environment:

```typescript
import { logger } from '@playcanvas/splat-transform';

logger.setLogger({
    log: console.log,
    warn: console.warn,
    error: console.error,
    debug: console.debug,
    progress: (text) => process.stdout.write(text),
    output: console.log
});

logger.setQuiet(true); // Suppress non-error output
```