Blackman window with the rounded coefficients {21 25 4}/50 on [-1/2 1/2]
BlackmanWindow[x]
Plot[BlackmanWindow[x], {x, -1, 1}]
→ -Graphics-Plot3D[BlackmanWindow[x]BlackmanWindow[y], {x, -1, 1}, {y, -1, 1}, PlotRange -> All]
→ -Graphics3D-BlackmanWindow[0.1]
→ 0.8492298567374695