O-Voxel is the field-free sparse voxel structure at the center of Microsoft TRELLIS.2. The project describes it as an “omni-voxel” representation that stores geometry and appearance for arbitrary 3D assets without forcing every result through an iso-surface field.
This matters because open surfaces, non-manifold geometry, and enclosed internal structures do not always fit the assumptions used by conventional surface-extraction pipelines.
Primary sources: TRELLIS.2 project page, repository, and research paper.
What O-Voxel represents
Microsoft documents O-Voxel as supporting:
- complex geometry and sharp features
- open surfaces such as clothing or leaves
- non-manifold geometry
- enclosed internal structures
- Base Color
- Roughness
- Metallic
- Opacity
Geometry and surface appearance live in the same native representation. That is the basis for TRELLIS.2's PBR-oriented output rather than an after-the-fact claim added by trellis2.com.
What “field-free” means
Many 3D pipelines describe a shape through a continuous field and later extract an iso-surface. That can be elegant for closed surfaces, but the surface-extraction assumption can become awkward for an open sheet, intersecting parts, or internal geometry.
TRELLIS.2's published claim is that O-Voxel breaks that iso-surface constraint. It should not be simplified into “an octree that stores occupancy probability” unless a source explicitly establishes that implementation detail.
Sparse does not mean low resolution
The model uses a Sparse 3D VAE with 16× spatial downsampling to encode assets into compact structured latents. Microsoft publishes output resolutions of:
- 512³
- 1024³
- 1536³
Sparse processing means the system does not treat every position in a dense 1536³ volume as an equally active element. It does not mean every generated asset has the same polygon count, file size, or topology quality.
O-Voxel and GLB export
The official example converts the generated O-Voxel mesh into a GLB with:
- vertices and faces
- attribute volume and layout
- decimation target
- texture size
- optional remeshing
The exported GLB uses OPAQUE mode by default. Although alpha remains in the texture, transparency must be enabled in the destination material when needed.
See the official usage example and our Blender export guide.
What O-Voxel does not prove by itself
The representation does not guarantee that every single-image result will have:
- a correct hidden side
- production-ready topology
- no floating or duplicated geometry
- physically correct materials
- zero cleanup
A single image leaves unseen geometry ambiguous. The representation expands what the model can express; output quality still depends on the input, inference model, settings, and acceptance criteria.
How to evaluate it
Use sources with thin parts, openings, overlapping surfaces, metallic/rough materials, and transparency cues. Then inspect the exported file rather than a turntable screenshot:
- rotate behind the object
- enable wireframe
- check non-manifold edges
- inspect UVs and material maps
- test opacity in the destination renderer
- record the selected resolution, texture size, remesh, and decimation settings