About generating a surface with curves

[olarreal-ozzy]

I have many 3d curves data  data1.data_1.dat, ..., data_N:
data_1.dat
x1_1 y1_1 z1_1
x2_1 y2_1 z2_1
..............
xn_m1 yn_m1 zn_m1

data_2.dat
x1_2 y1_2 z1_2
x2_2 y2_2 z2_2
..............
xn_m2 yn_m2 zn_m2

data_3.dat
x1_3 y1_3 z1_3
x2_3 y2_3 z2_3
..............
xn_m3 yn_m3 zn_m3

.
.
.
data_N.dat
x1_N y1_N z1_N
x2_N y2_N z2_N
..............
xn_N yn_N zn_N


How do I plot a surface generated by these curves with gnuplot?
I think that:
1. I have to compute: M=max{n_1,...,n_N}
2. I have to fill every data_k.dat by repeating the last row up to reach M rows

The best way to do so, is with awk?