MATLAB: How to plot a triangular shape function on a triangular domain

Question

Hello, I want to plot the following shape function: N(s,t)=t*(2*t-1) It has to look like the following diagramm:

but I get this one:

Here is my code:

[s,t]=meshgrid(0:0.1:1,0:0.1:1)
N3=@(s,t)t.*(2*t-1);
surf(s,t,N3(s,t))

I know that the problem is with the rectangular domain, that meshgrid generates. But I don't know how to define a triangular domain. Has anybody an idea?

Thanks

Answer 1

I described one approach in this thread.