Lanczos window Sinc[2 Pi x] on [-1/2 1/2] (radical multiples of 1/Pi at exact points)
LanczosWindow[x]
Plot[LanczosWindow[x], {x, -1, 1}]
→ -Graphics-Plot3D[LanczosWindow[x]LanczosWindow[y], {x, -1, 1}, {y, -1, 1}, PlotRange -> All, Exclusions -> None]
→ -Graphics3D-LanczosWindow[0.1]
→ 0.935489283788639