Nexus (.nxs / .nxz) — CNR-ISTI multiresolution mesh

Status: 🟠 doc-referenced only — no converter built (Nexus is a multiresolution mesh format, not Gaussian splats, and is comparatively niche). Listed for completeness / possible future work. Refs: https://github.com/cnr-isti-vclab/nexus · paper "Fast decompression for web-based view-dependent 3D rendering" (Ponchio & Dellepiane, 2016): https://vcg.isti.cnr.it/Publications/2016/PD16/FastDec_Ponchio.pdf

Gist

Nexus stores a multiresolution DAG of mesh patches built by batched multi-triangulation. A viewer traverses the DAG and selects a cut of patches to meet a screen-space error budget, streaming patches on demand (the .nxz variant adds per-patch geometry/color compression with fast GPU-side decode — the focus of the 2016 paper).

• Hierarchy: DAG of patches (not a strict tree); each node = a mesh chunk at some LoD.
• Content: triangle mesh (vertices/faces) + optional per-vertex color/normals/texcoords; not splats.
• Metadata: header + patch index (offsets/bounding spheres/errors) at the file head; patch data follows.
• HTTP: range-requestable (patches fetched individually), designed for web streaming.

Why no converter (yet)

This repo targets Gaussian-splat tiling → 3D Tiles KHR_gaussian_splatting. Nexus is mesh-based, so a nexus-to-3dtiles would emit b3dm/glTF mesh tiles, not splats — a different content path. Low demand; left as a reference. The DAG→tree mapping (pick a patch cut per SSE) maps conceptually onto 3D Tiles HLOD if ever needed.