What is a Geometry Kernel? C3D vs ACIS vs Parasolid
Why Hacker News recommends it
Cited in CAD threads as a rare plain-spoken comparison of commercial geometry kernels and their limitations.
What it is
The Plasticity creator explains what a geometry kernel is and compares commercial options C3D, ACIS, and Parasolid, describing his months of research and why he chose as he did.
Recommended by 3 HN commenters across 2 different months, 2023 to 2025.
What Hacker News said
Recommends s1mon · 2023-02 · on “CAD Sketcher, free and open-source project bringing CAD like tools to Blender3d”
Nick Kallen has been working on an BREP based CAD tool with the sort of ease of modeling that things like Blender has. Originally it was based on C3D, but he switched halfway through to Parasolid.[0] It’s amazing the amount of features he has built considering it’s a one person project. It’s worth going through his progress report videos.[1] [0] [this video] [1] [LINK]
Recommends virtualritz · 2023-02 · on “Show HN: Replicad, the Library for CAD in the Browser”
See also this thread[1] from yesterday which has some interesting comments on the limitations projects based on the OpenCascade kernel face. Mentions an interesting video[2] going through the commercial geometry kernel options and their resp. limitations from the author of [3]. [1] [LINK] [2] [this video] [3] [LINK]
Recommends awhitty · 2024-03 · on “Plasticity: CAD for Artists”
The creator of this app, Nick Kallen, has a nice YouTube channel where he talks about some of the behind-the-scenes work on the project. I think his video comparing geometry kernels [0] was posted to HN a while back, but it's worth a watch if you're curious! [0]: [this video]
Cites ruevs · 2025-06 · on “Show HN: Chili3d – A open-source, browser-based 3D CAD application”
The other "decent" commercial one that can be licensed is C3D (ASCON/АСКОН uses a CAD kernel based on it in КОМПАС 3D) but it is Russian and thus currently "behind sanctions". Here is a bit on it from the author of Plasticity: [this video] it initially was based on C3D.