Hamming window 25/46 + (21/46) Cos[2 Pi x] on [-1/2 1/2] (exact for exact input)
HammingWindow[x]
Plot[HammingWindow[x], {x, -1, 1}, Exclusions -> None]
→ -Graphics-Plot3D[HammingWindow[x]HammingWindow[y], {x, -1, 1}, {y, -1, 1}, PlotRange -> All, Exclusions -> None]
→ -Graphics3D-HammingWindow[0.1]
→ 0.9128121061276934