Compression
Draco Compression
Compress mesh geometry using KHR_draco_mesh_compression for significantly smaller geometry files.
Default: Off
glTF Extension: KHR_draco_mesh_compression
Draco is an open-source mesh compression library from Google. When enabled, geometry data is encoded with Draco before being written to the glTF file. This can significantly reduce the size of geometry, at the cost of requiring Draco support in any viewer or tool that opens the file.
Presets
Start with a preset to set all sliders at once. Adjusting any individual slider afterwards automatically switches to Custom.
| Preset | Compression Level | Position Bits | Typical use |
|---|---|---|---|
| Fast | 2 | 18 | Quick testing — largest output, fastest encoding |
| Balanced | 7 | 14 | Default tradeoff between quality and file size (default) |
| High | 9 | 12 | Stronger compression, slight geometry precision cost |
| Maximum | 10 | 11 | Smallest output — use when size is critical |
| Custom | Manual | Manual | Full per-attribute control |
Strip Uncompressed
Default: On
When enabled, the original uncompressed vertex data is removed from the file — only the Draco-compressed version is kept.
- Leave it on to get the full size benefit of Draco
- Turn it off only if a specific downstream tool needs both the compressed and uncompressed vertex data to be present simultaneously
Advanced Controls
These sliders are fully accessible in Custom preset and are also adjusted automatically when you apply other presets.
Compression Level
- Range: 0–10 · Default: 7
- Controls how much effort the Draco encoder applies
- Higher values produce smaller files but take longer to encode; lower values are faster with larger output
Quantization Sliders
Each slider controls how many bits are used to store that vertex attribute. More bits means more precision and slightly larger files.
| Attribute | Default | What it stores |
|---|---|---|
| Position Bits | 14 | Vertex world position |
| Normal Bits | 10 | Surface normal direction |
| Texcoord Bits | 12 | UV coordinates |
| Color Bits | 8 | Vertex color values |
| Generic Bits | 8 | Other custom vertex attributes |
Practical guidance:
- Position Bits — reduce carefully; geometry shift becomes visible at lower values, especially on tight-fitting meshes
- Normal Bits — reducing below 8 can cause banding in smooth lighting; 10 is a safe minimum
- Texcoord Bits — 10–12 is usually safe for most textures; lower values may shift UV seams
Warning
Draco is marked as required in the exported file. Viewers and tools that do not support KHR_draco_mesh_compression will refuse to open the file. Always confirm runtime support before shipping Draco-compressed assets.