Linear Time-Variant System

I've only dealt with linear time-invariant systems in the past, so when I was presented with this sort of system I thought it would helpful to try and plot it. Given this system now has two independent variables it's helpful to take a look at it using a three dimensional plot.

f = 5;
fs = 128;
dt = 1/fs;
N = fs;
t = 1/fs*(0:N-1);

T = 0.05;
[t, tau] = meshgrid(t, linspace(0, T, N));
h = (1 - tau/T) * cos(2*pi*f*t);
mesh(t, tau, h), xlabel('t'), ylabel('tau'), axis('square')
title('LTV System')