BLD · Classicery

BUILD · 1973

A clean-room reconstruction of Ian C. Braid's B-rep solid modeler, presented at the PROLAMAT conference in Budapest, 1973. Developed at the Cambridge University Computer Laboratory CAD Group under Charles Lang.

BUILD was the first system to demonstrate that boundary representation — describing a solid by its closed surface of faces, edges, and vertices — was both mathematically sound and computationally tractable. Boolean operations (union, difference, intersection) on polyhedral solids were computed on Cambridge's Titan mainframe.

The commercial lineage runs directly through Shape Data (1974) → ROMULUS (1978) → Parasolid → SolidWorks, NX, Solid Edge. Every major commercial B-rep kernel in production CAD today traces to this thesis.

Four rooms in Classicery touch 3D: SP (1963, light-pen constraint sketch), SV (1972, CSG ray casting, the sibling on the other side of PROLAMAT 1973), BLD (1973, this room, B-rep solid modeling), ALYUS (1985, Cardinal-spline surfaces). Chapter 8 inside reads the four together.

TYPE HELP AT THE PROMPT · DRAG THE VIEWPORT TO ORBIT

This is a clone, not the original. BLD is a clean-room recreation of Cambridge BUILD (1973) — no proprietary code, assets, screenshots, or fonts. BUILD, Parasolid, ACIS, SolidWorks, NX, Solid Edge, CATIA and all other named systems and products are trademarks of their respective owners. Classicery and Phil Renato claim no trademark or copyright interest in any of them and are not affiliated with, endorsed by, or sponsored by the University of Cambridge, Siemens, Spatial Corp / Dassault Systèmes, Shape Data, or any of their successors.

FROM THE LITERATURE · B-rep is one of two answers to the question Catmull and Clark would re-pose five years later: how to converge a cage onto a smooth surface. Hear the source paper read aloud in CANON · 001B:
→ track 09 · Catmull-Clark · Subdivision Surfaces · 1978