MeshTools::all_rbb() to generate IGA rational quadratic meshes#4442
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This takes an interpolated quadratic Lagrange mesh and turns it into an IGA (Rational Bezier-Bernstein) mapped mesh, assuming that all curves are intended to be circular/cylindrical/spherical.
1D on the X axis is pointless, but 1D meshes embedded in 2D or 3D space may still benefit from perfect circles.
This still gets us isogeometry on aligned cylinders, but also on cones and some types of spheres, and gets us a sort of optimality on non-exactly-representable surfaces.
It's the same either way but it just read wrong the other way.
I was about to stop capturing it, to fix an unused var warning, but this is better.
GiudGiud
reviewed
May 21, 2026
Thanks to Guillaume for catching these
This is still a hack I'm working on replacing, but now it's a *slightly faster* hack!
Just because it's trivial doesn't definitely mean it's not broken!
Even a p=1 face can have a different volume if the vertex weights differ and the face is embedded in 3D with non-coplanar vertices.
I'm not sure when we'll try using RBB polygons, but if we started now we actually wouldn't need the specialization for this one.
The R part is working but I didn't realize we'd never implemented the BB part, and that'll be a separate PR.
I was trying to be clever with my if statements but I was missing out on all sorts of complications; the code was fine but the tests weren't even close.
GiudGiud
reviewed
May 24, 2026
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btw I can't resolve threads with this level of permissions either |
This is more robust in general, plus I need it to get a robust Hex27 solution
Glad that clang++ caught this!
GiudGiud
approved these changes
May 26, 2026
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This needs proper test coverage before merging but I've been letting it sit in a separate branch for too long and I want to at least make sure it's not interfering with any CI builds.