Obj2Tiles - Converts OBJ file to 3D Tiles format

Obj2Tiles is a fully-featured tool to convert OBJ files to 3D Tiles format. It runs a three-stage pipeline: Decimation → Splitting → Tiling, creating multiple LODs, splitting the mesh into spatial tiles, and repacking textures.

Community

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Installation

You can download precompiled binaries for Windows, Linux and macOS from https://github.com/OpenDroneMap/Obj2Tiles/releases.

Usage

Obj2Tiles [options] <input.obj> <output>

<output> is either a folder (a loose tileset.json + tiles tree) or a path ending in .3tz, which produces a single 3D Tiles Archive file.

Command line parameters

Input / Output

Parameter	Default	Description	Example
Input (pos. 0)		Input OBJ file (required)	model.obj
Output (pos. 1)		Output folder, or a .3tz file for a single 3D Tiles Archive (required)	./tileset-output or model.3tz

Pipeline Control

Parameter	Default	Description	Example
-s, --stage	Tiling	Stage to stop at: Decimation, Splitting, or Tiling	--stage Splitting
-l, --lods	3	Number of levels of detail to generate	--lods 5

Splitting

Parameter	Default	Description	Example
-d, --divisions	2	Recursion depth for binary splitting along each axis. Each level doubles the grid, producing (2^divisions)^2 tiles along XY (or (2^divisions)^3 with --zsplit). For example, --divisions 2 gives a 4x4 grid (16 tiles) and --divisions 3 gives 8x8 (64 tiles)	--divisions 3
-z, --zsplit	false	Also split along the Z-axis (not just X and Y)	--zsplit
-g, --split-strategy	VertexBaricenter	How the split point is computed: AbsoluteCenter (bounding box center), VertexBaricenter (vertex average), or VertexMedian (vertex median, most balanced)	--split-strategy VertexMedian
-k, --keeptextures	false	Keep original textures instead of repacking them (not recommended)	--keeptextures
--octree	false	Use octree spatial subdivision: each LOD gets one additional division level, producing a proper parent-child tile hierarchy instead of per-tile LOD chains. Combine with --zsplit for a true 8-way octree	--octree --zsplit
--lod-texture-scale	0.5	Per-LOD texture downscale factor. LOD-0 always keeps full resolution; each subsequent LOD multiplies the previous atlas resolution by this factor. E.g. 0.5 gives LOD-1 at half resolution, LOD-2 at quarter, etc. Uses bicubic resampling	--lod-texture-scale 0.5

Textures

Controls how repacked texture atlases are encoded.

Parameter	Default	Description	Example
--texture-format	Jpeg	Output format for repacked textures: Jpeg (default), Webp (25-35% smaller, emits EXT_texture_webp), or Ktx2 (GPU-compressed Basis Universal, emits KHR_texture_basisu, cuts VRAM 4-8x - see KTX2 GPU Texture Compression)	--texture-format Ktx2
--texture-quality	75	JPEG/WebP quality (1-100). Higher is better quality but larger files. Only for Jpeg and Webp formats	--texture-quality 90
--max-texture-size	4096	Maximum texture atlas resolution per side (pixels). Source textures larger than this are downscaled. 0 disables the cap	--max-texture-size 2048
--ktx2-quality	128	KTX2 ETC1S/BasisLZ quality (1-255; higher = better quality, larger files). Reinterpreted as UASTC quality (0-4) when --ktx2-uastc is set. Only used with --texture-format Ktx2	--ktx2-quality 200
--ktx2-uastc	false	Use UASTC instead of ETC1S/BasisLZ for KTX2 textures. UASTC transcodes to BC7/ASTC for near-lossless quality at ~3x the size of ETC1S. Only used with --texture-format Ktx2	--ktx2-uastc
--ktx-path		Path to the libktx native library or its directory. When omitted, resolved from OBJ2TILES_KTX, then the executable directory (where the bundled lib lives), then system PATH. Only used with --texture-format Ktx2	--ktx-path /usr/lib/libktx.so

Geo-referencing

Parameter	Default	Description	Example
--lat		Latitude in WGS84 decimal degrees	--lat 45.4642
--lon		Longitude in WGS84 decimal degrees	--lon 9.1903
--alt	0	Altitude in meters above the WGS84 ellipsoid	--alt 120
--scale	1	Scale factor for local geometry (e.g. 1200.0/3937.0 for survey feet). Does NOT affect altitude or ECEF position	--scale 0.3048
--local	false	Local mode: no ECEF geo-referencing, uses an identity matrix. Use when you don't need globe placement	--local
--y-up-to-z-up	false	Apply a 90° rotation around the X-axis to convert Y-up OBJ files to Z-up (3D Tiles convention)	--y-up-to-z-up

Output format

By default Obj2Tiles writes a loose folder tree (tileset.json, LOD-*/ and root.b3dm). It can instead pack everything into a single 3D Tiles Archive (.3tz) file - a ZIP container defined by the 3TZ specification. The archive embeds a trailing @3dtilesIndex1@ index so viewers can random-access individual tiles without unpacking it. .3tz output is selected automatically when the output path ends with .3tz, or explicitly with --3tz.

Parameter	Default	Description	Example
--3tz	false	Produce a single .3tz archive instead of a folder tree (implied by a .3tz output path). When set without a .3tz extension, the archive is written to <output>.3tz	--3tz
--3tz-compression	6	DEFLATE level for .3tz content, 0-9 (gzip-style), see table below. The index is always stored uncompressed	--3tz-compression 9

Compression levels (--3tz-compression):

Value	Effect
0	Stored (no compression) - fastest reads, largest file
1-3	Fastest DEFLATE
4-6	Balanced DEFLATE (default 6)
7-9	Smallest DEFLATE

Notes: .3tz output requires the full Tiling stage (it cannot be combined with --stage Decimation/Splitting). Archives and individual files must stay below 4 GB (ZIP64 is not emitted). Zstandard compression (allowed by the 3TZ spec) is planned for a future release.

Other

Parameter	Default	Description	Example
-e, --error	0 (auto)	Base geometric error for the root tile in tileset.json. When 0 (default) it is derived automatically from the model's bounding box diagonal	--error 500
--use-system-temp	false	Use the system temp folder for intermediate files instead of the output folder	--use-system-temp
--keep-intermediate	false	Keep intermediate files (decimated OBJs, split tiles) for debugging	--keep-intermediate
--help		Display help screen	--help
--version		Display version information	--version

Pipeline Stages

1. Decimation

The source OBJ is decimated using the Fast Quadric Mesh Simplification algorithm by Mattias Edlund (ported from .NET Framework 3.5 to .NET Core; original repo here).

The number of LODs is controlled by --lods. Decimation quality levels follow this formula:

quality[i] = 1 - ((i + 1) / lods)

For example, with 5 LODs the quality levels are: LOD-0 is the original (100%), followed by 80%, 60%, 40%, 20%. If you specify 1 LOD, decimation is skipped entirely.

2. Splitting

For every decimated mesh, the program splits it recursively along the X and Y axes (and optionally Z with --zsplit). Each split produces a new mesh with repacked textures using the MaxRects bin packing algorithm by Jukka Jylänki.

Split strategies (--split-strategy):

• VertexBaricenter (default): split point is the barycenter of the sub-mesh vertices. Adapts to geometry concentration, producing balanced tiles.
• AbsoluteCenter: split point is the bounding box center. Produces a spatially uniform grid but may yield uneven tiles for non-uniform geometry.
• VertexMedian: split point is the vertex median. Most balanced of all strategies - robust to outliers and skewed distributions. Uses a pre-computed split plan from LOD-0 vertices so all LODs share the same split points without redundant computation.

Octree mode (--octree):

By default, every LOD produces the same number of tiles arranged as per-tile chains in tileset.json. With --octree, each LOD receives one additional division level compared to the next coarser LOD. The per-LOD split depth formula is lodDivisions = divisions + lods - index - 1 (fine LODs get deeper splits). The grid at depth D is $(2^D)^2$ tiles:

LOD	LOD depth (--divisions 2, 3 LODs)	Grid	Tiles (XY)
0 (finest)	2+3-0-1 = 4	16x16	256
1	2+3-1-1 = 3	8x8	64
2 (coarsest)	2+3-2-1 = 2	4x4	16

Coarser tiles become spatial parents of finer ones in tileset.json, producing a proper tree hierarchy. Combine --octree with --zsplit for a true 8-way octree.

Texture downscaling (--lod-texture-scale):

Each tile's texture atlas is repacked from the portion of the source texture within that tile. Use --lod-texture-scale to reduce atlas resolution for coarser LODs:

LOD	Scale (--lod-texture-scale 0.5)	Example atlas (4096×4096 source, 16 tiles)
0 (finest)	1.0 (always full)	1024×1024 (original format)
1	0.5	512×512 JPEG
2	0.25	256×256 JPEG

Downscaling uses ImageSharp's default resampler. LOD-0 preserves the original texture format; coarser LODs are JPEG at quality 75.

3. Tiling

Each split mesh is converted to B3DM (3D Tiles) format via an OBJ → glTF → GLB → B3DM conversion pipeline. Then tileset.json is generated with bounding volumes, geometric errors, and the ECEF transform matrix.

Coordinate system & geo-referencing:

The tiling stage places the model on the globe using an ECEF (Earth-Centered, Earth-Fixed) transformation matrix in tileset.json.

Flags	Behavior
--lat 45 --lon 9 --alt 100	Full ECEF transform at the given WGS84 coordinates
(no lat/lon)	Falls back to default coordinates (Duomo di Milano, 45.46°N 9.19°E)
--local	Identity matrix - no geo-referencing. Use for local viewers

Important notes:

• --scale only affects local geometry size, not altitude or ECEF position. --scale 100 --alt 17 places the model at 17 meters, not 1700.
• OBJ files typically use Y-up. Bounding volumes in tileset.json perform a Y↔Z swap internally (3D Tiles uses Z-up). If the model appears flipped, try --y-up-to-z-up for an additional 90° X-axis rotation.
• --local takes precedence over --lat/--lon (a warning is printed if both are specified).

Output format: the tileset is written either as a loose folder tree or as a single .3tz archive - see Output format.

KTX2 GPU Texture Compression

The --texture-format Ktx2 option encodes every texture atlas as KTX2 with Basis Universal supercompression (KHR_texture_basisu) instead of JPEG. This lets the GPU decompress and store the texture natively, reducing VRAM usage by 4-8x and cutting draw-call overhead compared to JPEG atlases.

Two compression modes:

Mode	Flag	Quality range	Transcodes to	Best for
ETC1S / BasisLZ (default)	(none)	--ktx2-quality 1-255	ETC2, BC1/BC3, PVRTC	Smallest files, maximum hardware compatibility
UASTC	--ktx2-uastc	--ktx2-quality 0-4	BC7, ASTC, ETC2	Near-lossless quality, ~3x larger than ETC1S

Renderer requirements:

Not all renderers support KHR_texture_basisu. Verified to work: CesiumJS, CesiumNative, Babylon.js, three.js (with KTX2Loader), and most WebGPU-capable renderers. Use --texture-format Jpeg (the default) for environments where KHR_texture_basisu support is uncertain.

Bundled native library (libktx)

Encoding runs in-process via the KTX-Software C library (libktx v4.4.2, Apache-2.0) through P/Invoke - no external tool is executed and no installation is required. The published single-file binaries bundle the matching native library for each platform:

Platform	File	Size
Windows x64	ktx.dll	2.31 MB
Windows ARM64	ktx.dll	1.94 MB
Linux x64	libktx.so	3.25 MB
Linux ARM64	libktx.so	2.91 MB
macOS x64	libktx.dylib	2.67 MB

For dotnet build without a RID (development builds), the library is resolved in order from: --ktx-path / OBJ2TILES_KTX environment variable, the executable directory, and finally the system PATH.

Updating libktx

To refresh the vendored libraries to a new KTX-Software release, run the PowerShell script bundled in the repository:

# Refresh all 5 platforms to the default version
pwsh Obj2Tiles/native/update-libktx.ps1

# Bump to a new version
pwsh Obj2Tiles/native/update-libktx.ps1 -Version 4.5.0

# Refresh only Linux and macOS (no 7-Zip required)
pwsh Obj2Tiles/native/update-libktx.ps1 -Rid linux-x64,linux-arm64,osx-x64

# Skip checksum verification
pwsh Obj2Tiles/native/update-libktx.ps1 -SkipChecksum

Requirements:

• PowerShell 7+ (pwsh) - available on Windows, Linux, and macOS
• tar (included with Windows 10+, Linux, macOS) - used for Linux tarballs and the macOS .pkg
• 7-Zip - required only for the Windows NSIS .exe installers. Install with winget install 7zip.7zip, choco install 7zip, apt-get install p7zip-full, or brew install p7zip
• Optional: set $env:GITHUB_TOKEN to raise the anonymous GitHub API rate limit

The script queries the GitHub release API to resolve download URLs and SHA-256 digests, downloads each platform asset, verifies integrity, extracts the native library, and copies it into Obj2Tiles/native/<rid>/ with the correct filename. After updating, rebuild and re-publish to include the new library in the single-file executable. Also update the source-mapping comment in Obj2Tiles/Obj2Tiles.csproj.

Examples

You can download a test OBJ file here (Brighton Beach textured model generated with OpenDroneMap).

Basic usage (defaults)

Run all pipeline stages and generate tileset.json in the output folder:

Obj2Tiles model.obj ./output

3D Tiles Archive (.3tz)

Pack the whole tileset into a single archive (selected by the .3tz extension) with maximum compression:

Obj2Tiles --3tz-compression 9 model.obj ./model.3tz

KTX2 GPU-compressed textures

Encode every texture atlas as Basis Universal KTX2 for minimal VRAM consumption (ETC1S mode, quality 192):

Obj2Tiles --texture-format Ktx2 --ktx2-quality 192 --local model.obj ./output

UASTC mode for near-lossless quality targeting BC7/ASTC renderers (larger files):

Obj2Tiles --texture-format Ktx2 --ktx2-uastc --ktx2-quality 3 --local model.obj ./output

Cap atlas size to 2048 px and raise JPEG quality for the default format:

Obj2Tiles --max-texture-size 2048 --texture-quality 90 --local model.obj ./output

Octree with texture downscaling (recommended for large models)

Produce a proper octree hierarchy with textures halved at each LOD step:

Obj2Tiles --octree --zsplit --lods 3 --divisions 2 --lod-texture-scale 0.5 --local model.obj ./output

Geo-referenced model

Place the model at specific GPS coordinates with 8 LODs and 3 levels of binary splitting (8x8 grid, 64 tiles):

Obj2Tiles --lods 8 --divisions 3 --lat 40.6894 --lon -74.0445 --alt 120 model.obj ./output

Stop at decimation stage

Generate 8 decimated LODs without splitting or tiling:

Obj2Tiles --stage Decimation --lods 8 model.obj ./output

Stop at splitting stage

Generate split tiles with 3 levels of binary splitting (8x8 grid, 64 tiles):

Obj2Tiles --stage Splitting --divisions 3 model.obj ./output

Local mode (no geo-referencing)

For local 3D viewers that don't need globe placement:

Obj2Tiles --local model.obj ./output

Balanced splitting with VertexMedian

Use the median-based split strategy for the most balanced tiles:

Obj2Tiles --split-strategy VertexMedian --lods 4 --divisions 2 --local model.obj ./output

Survey feet to meters

Scale geometry from survey feet to meters:

Obj2Tiles --scale 0.3048 --lat 45.0 --lon 9.0 --alt 0 model.obj ./output

Running

Obj2Tiles is built using .NET 10.0. Binary releases are available on GitHub for Windows, Linux, and macOS.

Download the latest release or compile from source:

git clone https://github.com/OpenDroneMap/Obj2Tiles.git
cd Obj2Tiles
dotnet build -c Release

Docker

A Docker image is available for Linux (x64 and arm64) with a multi-stage build and trimming for minimal runtime footprint:

docker run --rm -v $(pwd):/data ghcr.io/opendronemap/obj2tiles model.obj /data/output

Or build locally:

docker build -t obj2tiles .
docker run --rm -v $(pwd):/data obj2tiles model.obj /data/output

Rotating the model

After generating tileset.json, you can edit the 4x4 Transform matrix to add translation, rotation, and scaling. This is the matrix structure:

The tiling stage uses this matrix to place the model at the requested geo location:

You can add scaling:

Or rotation around any of the 3 axes:

By combining these matrices, you can rotate, scale, and translate the model. More details on BrainVoyager.

OBJ Format Support

The OBJ parser handles the following format features:

• Vertex formats: v x y z and v x y z r g b (vertex colors)
• Face formats: f v/vt/vn, f v//vn, f v/vt, and f v (geometry only)
• Quads and n-gons: Automatically triangulated using fan triangulation (Issue #60)
• Line elements: Gracefully skipped (Issue #64)
• Scientific notation: Coordinates like 1.5e-3 are parsed correctly
• UV wrapping: Texture coordinates outside [0,1] are wrapped for UDIM/mirroring workflows (Issue #35)
• MTL options: Full support for -bm, -blendu, -blendv, -boost, -cc, -clamp, -imfchan, -mm, -texres, -type, -o, -s, -t and other material map options
• Path resolution: Textures are resolved by progressively relaxing the base directory (MTL folder, OBJ folder, absolute path)

Remarks

• All pipeline stages are multi-threaded for performance. Tile writing runs in parallel.
• Stop the pipeline at any stage with the --stage flag.
• Keep intermediate files with --keep-intermediate for debugging.
• Use --use-system-temp to store intermediate files in the system temp folder.

Gallery