TripoSR — ONNX export
ONNX re-export of stabilityai/TripoSR (Tripo AI + Stability AI — MIT code + MIT weights): single-image → 3D reconstruction via a triplane radiance field. All credit for the original weights goes to Tripo AI and Stability AI.
Exported for QtMeshEditor
(epic #764), powering qtmesh generate3d, the Inspector's AI: Image → 3D
section, and the generate_mesh_from_image MCP tool — local inference via
ONNX Runtime, with surface extraction done by a native marching-cubes
implementation (upstream's torchmcubes is torch/GPU-only).
The files QtMeshEditor downloads at runtime live in the shared
fernandotonon/QtMeshEditor-modelsrepo undertriposr/. This repo is the standalone model card + mirror.
Files
| file | role |
|---|---|
triposr_encoder.onnx | fp32 encoder (best quality, ~1.7 GB): image [1,3,512,512] → scene_codes [1,3,40,64,64] (triplane) |
triposr_encoder_int8.onnx | int8 encoder tier (~430 MB, slight quality loss) |
triposr_decoder.onnx | per-point field decoder: scene_codes + points [1,P,3] → density [1,P,1], color [1,P,3] |
An fp16 tier is deliberately absent: TripoSR's attention has a hardcoded Cast-to-float32 that the ONNX fp16 converters cannot rewrite.
Inference contract
- Input image: 512×512 RGB in
[0,1], subject isolated (upstream composites over gray-128 and re-pads the foreground to a 0.85 ratio; QtMeshEditor uses U²-Net for background removal first). - Query the decoder in chunks — generating the full
res³grid up front OOMs at high resolutions. - Surface = marching cubes on
density − thresholdat iso 0, threshold 25.0, within radius 0.87. The field is inside-positive; emit flipped winding (v0,v2,v1) to keep faces outward. - Output is not +Y-up: bake −90°X then +90°Y to stand the model upright facing forward.
- The decoder's colour output can also be used as an image-conditioned colour field for texture baking (per-texel queries after a UV unwrap).
Reproducing
scripts/export-triposr-onnx.py in the QtMeshEditor repo (one-time, offline;
transformers==4.35.0, torchmcubes stubbed, frozen ViT positional
encoding; emits the int8 variant unless --no-quant).
License
MIT (same as the upstream code and weights). Credit: Tripo AI + Stability AI.