How to draw a three-dimensional function image corresponding to the analytic expression of a given piecewise function image

How do I draw this image in code

Answer 1

[Torsten]

f = @(x,y)(4*y-4*x.*y-2*y.^2).*(y<x).*(x+y<1)+2*(1-x).^2.*(y<x).*(x+y>=1)+(4*y-4*y.^2-2*x.^2).*(y>=x).*(x+y<1)+(2-4*x+4*x.*y-2*y.^2).*(y>=x).*(x+y>=1);
nx = 20;
ny = 40;
x = linspace(0,1,nx);
y = linspace(0,1,ny);
[X,Y] = meshgrid(x,y);
surf(X,Y,f(X,Y))

[立达]

Thanks！！！