How do I define this without using piecewise function?
I think it has something to do with Bilinear Surface but not sure how to get started.
$x_1=-1, x_2=1, x_3=0, x_4=1$
$y_1=0, y_2=1, y_3=1, y_4=0$
I don't understand what is this $u & v$ we have here.