num::sample_2d_periodic

Defined in header <pde/stencil.hpp>

real sample_2d_periodic(const vec<real> &field, idx N, real h, real px, real py,
                        real ox, real oy);  // (1)

real sample_2d_periodic(const scalar_field_2d &g, real px, real py, real ox = 0.0,
                        real oy = 0.0);  // (2)

Bilinear interpolation on a periodic NxN grid with a stagger offset.

field[i,j] sits at physical position (ih + ox, jh + oy). On a MAC grid, u takes (ox, oy) = (0, h/2) and v takes (h/2, 0).

Parameters

• field: Flattened grid samples.
• N: Grid width and height.
• h: Grid spacing.
• px: Physical x coordinate.
• py: Physical y coordinate.
• ox: x offset in physical units.
• oy: y offset in physical units.