How to plot over another surface?

So here is my code

N=6; V is a matrix which is 6x6

[X, Y] = meshgrid (1: N, 1: N);

surf (X, Y, V);

With this code, one plots in Matlab a scalar field over a square surface. How to plot over another surface (triangle, for example)

Answer 1

[madhan ravi]

hold on % after first surf() command