# Key Points from IRC Conversation

• OpenCascade, an open-source CAD software kernel, was extensively analyzed by users who documented its package structure and architecture, noting that much of the core geometry code dates to the late 80s/early 90s, with later development focusing more on document frameworks than core functionality.

• The conversation revealed technical issues with OpenCascade's organization, including the parallel existence of both old and new Boolean Operations packages (BOA and NBOA), raising concerns about code quality and integration challenges.

• Users discussed the licensing evolution of OpenCascade to LGPL and its contributor license agreement requirements, which led to the creation of a community edition fork (OCE) that periodically merges upstream changes.

• The technical discussion explored different geometry representation approaches in CAD software, comparing implicit geometry, Bezier curves, NURBS, and B-splines, with debate about their mathematical foundations and practical implementations.

• Participants traced the historical development of CAD systems, including Euclid (developed since 1970 at LIMSI and later acquired by Matra Datavision), highlighting how Russian and French developers contributed significantly to advanced computational geometry.

• A controversy was noted regarding B9 Creator, a supposedly "open source printer" company that sent cease and desist letters over a vat patent, contradicting their open-source marketing claims.

• The conversation concluded with technical discussion about two-photon DLP photolithography and whether digital micromirror devices (DMDs) could be effectively used for directing light in this process, considering diffraction limits and current techniques.