FreeMVD: Extrusions with Circles
Ongoing Results: https://github.com/OpeningDesign/FreeMVD_WorkFlow/blob/master/IFC_roundtrip_specifications.md#extrusions_circles
Test Files: https://github.com/OpeningDesign/FreeMVD_WorkFlow/tree/master/Specifications_Test_Files/Extrusions_Circles
FreeMVD: Are experiments on how well certain objects roundtrip in/out of various BIM applications. We are always looking for volunteers, from other BIM applications, to add their results to these tests. If you can participate, ping @yorik or @theoryshaw and they can give you Github push privileges.
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BlenderBIM: circles are faceted
https://gitlab.com/osarch/FreeMVD_WorkFlow/-/commit/d265a26649cd843c56fcc449952bf44c7ef03cbf
Circles will always be faceted in Blender, I think, it's just the nature of meshes, but when I build support for it, I do plan to retain the appropriate circle properties, which is the important part.
The BlenderBIM Add-on should now support importing circle profiles: https://github.com/IfcOpenShell/IfcOpenShell/commit/75b34b6a952771702eaf546d1a7149be90967f39
Cool. Just import, or export too?
Export is now supported: https://github.com/IfcOpenShell/IfcOpenShell/commit/a66b4f138a6e558ec35a6b27e5dcf2934ea31556
blender has no real support for curves. there are nurbs, but it's not really used for modelling, it's more there to define animation paths and things like that. But it's not necessarily a problem. I see this like bitmap vs vector drawing. sometimes one is best, sometimes the other. and sometimes it would be really easy to "convert back", ex. you can really easily find a circle from a series of points placed equally around a common center (we should implement that in freecad..). and if you look at a cylinder in elevation in blender, it even renders the way we traditionally drew curved surfaces, with parallel lines closer to each other as the curvature grows :)
It's like with bitmap, with enough resolution, it ceases to be a problem
BlenderBIM results: https://gitlab.com/osarch/FreeMVD_WorkFlow/-/blob/7c1de28461e8a12b772fa879fb51d2713a2e6440/IFC_roundtrip_specifications.md#results-1
@theoryshaw the radius value is implicitly stored in the mesh - the circle facet will always have a multiple of 4 vertices, this allows you to therefore always reliably re-derive the radius easily by measuring, even in its faceted form - it will give the correct radius / diameter no matter which vertice you pick.