For 3d plot gnuplot use command splot.

splot sin(sqrt((x*x+y*y)))/sqrt(x*x+y*y) t "weaves"

Gnuplot surface wireframeGnuplot surface wireframe

We can add the style pm3d to add a gradient surface texture

splot sin(sqrt((x*x+y*y)))/sqrt(x*x+y*y) with pm3d t "weaves"

Gnuplot surface 3d pm3dGnuplot surface 3d pm3d

But you can see we need more resolution, then we must set more isosamples:

set isosamples 75,75

Gnuplot surface with pm3d and isosample 75,75Gnuplot surface with pm3d and isosample 75,75

For more info go to gnuplot page