What is a Geometry Kernel? C3D vs ACIS vs Parasolid

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.

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

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

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