Hua Tong - 2018-01-10

I want to plot polygons with filled color according to some variable defined, e.g., in third column.
In short, the data format is as below:
0.16658205E+02 0.29610505E+02 0.13685260E+01 1
0.15732364E+02 0.29916967E+02 0.13685260E+01 1
0.15111388E+02 0.28956940E+02 0.13685260E+01 1
0.16658205E+02 0.29610505E+02 0.13685260E+01 1

0.12330652E+02 0.32410390E+02 0.13104752E+01 2
0.11806368E+02 0.31577728E+02 0.13104752E+01 2
0.12629825E+02 0.30750973E+02 0.13104752E+01 2
0.12330652E+02 0.32410390E+02 0.13104752E+01 2
......
The command that I use is as below:
p "data" u 1:2:3 w filledcurves closed fillcolor palette
What I get is that the edge of each polygon is colored according to the third column, but not the filled color.

I searched and found this https://sourceforge.net/p/gnuplot/feature-requests/411/, where someone seemed to have the same problem but solution is not clear.

Since this function seems to be "Status: closed-fixed", I think solution is somewhere.

Thanks in advance!