fix: apply chain rule in StructuredGrid2D element gradient - #293
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StructuredGrid2D.get_element_gradient_for_location returned shape-function derivatives with respect to local (0-1) cell coordinates, so gradients were inflated by step_vector on each axis and became resolution-dependent. Mirror the division by step_vector that StructuredGrid3D already does. Fixes Loop3D#289
lachlangrose
approved these changes
Aug 4, 2026
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Fixes #289
StructuredGrid2D.get_element_gradient_for_locationreturned the shape-function derivatives with respect to local (0-1) cell coordinates, so gradients came out multiplied bystep_vectoron each axis and were silently resolution-dependent (directionally biased for anisotropic cells). This mirrors the division bystep_vectorthatStructuredGrid3Dalready does at the end of its implementation.Added two regression tests in
test_2d_discrete_support.py: a support-level check with anisotropic cells asserting unit gradients in world units, and an FDI-level check (condensed from the issue's reproducer) asserting the interpolated gradient magnitude stays ~1 across two resolutions. Full test suite passes locally (708 passed).