geometry-rendering

# geometry-rendering Use this sub-skill for the geometry side of 3DDFA: parameter reconstruction, ROI-to-image conversion, sparse and dense vertices, mesh serialization, pose matrices, depth/PNCC/PAF outputs, and the Cython-backed render path. ## Use when - you have a 62-D parameter vector or cropped ROI and need 68 landmarks or dense vertices; - you need PLY, OBJ, `.mat`, depth, PNCC, PAF, or pose artifacts; - you need to build or troubleshoot `utils.cython`; - you need dense render or video assembly helpers. ## Start here - [API reference](references/api-reference.md) - [Output formats](references/output-formats.md) - [Rendering and Cython](references/rendering-and-cython.md) - [Data artifacts](references/data-artifacts.md) - [Troubleshooting](references/troubleshooting.md) ## Bundled helpers - [scripts/smoke_geometry.py](scripts/smoke_geometry.py) - [scripts/images_to_video.py](scripts/images_to_video.py) ## Route elsewhere - Full detector/model inference and CLI flags belong in the sibling inference sub-skill. - Training losses, benchmark scripts, and dataset preparation belong in the training sub-skill. - ONNX export and the C++ port belong in the C++ sub-skill. ## Working facts - `utils.ddfa.reconstruct_vertex` is the canonical 3DMM reconstruction entry point. - The verified smoke for a zero 62-D vector returns sparse `(3, 68)` and dense `(3, 53215)` vertices. - `visualize/tri.mat` provides the triangle indices used by the renderer paths. - `utils.render` and `utils.lighting` depend on the compiled `mesh_core_cython` extension.