Months later, in a classroom hung with posters of measurement techniques, Serge led a class of wide-eyed twelve-year-olds through the basics of uncertainty. He demonstrated with a coin, a string, and a borrowed kitchen scale, narrating the thought process aloud: make independent measures, compare them, note biases, and never hide your mistakes. A hand shot up.
| Source | Content | Format | Cost | |--------|---------|--------|------| | | Aerospace brackets, turbine blades | STL, XYZ | Free | | AICON 3D Benchmarks | Prismatic parts with holes | PLY, CSV | Free | | GOM (Zeiss) Test Objects | Reference spheres & freeform surfaces | G3D, STL | Free with registration | | Thingiverse "Metrology Contest" | User-submitted gauge blocks | STL | Free | | Serge3DX (via Wayback Machine) | Historical contest scans | TXT, OBJ | Possibly archived free | file serge3dxmeasuringcontestandprincipa free
# Compute PCA (Principal Component Analysis) centroid = vertices.mean(axis=0) centered = vertices - centroid cov = np.cov(centered.T) eigenvalues, eigenvectors = np.linalg.eig(cov) Months later, in a classroom hung with posters