Plotting multiple 2D alphaShape polygons with different z-values

I am trying to plot multiple 2D alphaShape polygons with different z-offsets.

Method I tried:

Since 2D alphaShape objects do not have z values, I attempted to add an array of constant z values alongside the x and y values and recreate the polygon with alphaShape. When I tried plotting it, it does not work.

I would greatly appreciate any help regarding this

shp = alphaShape(x_wkspace',y_wkspace',1);
vertices = shp.Points;
phi_array = ones(length(vertices),1) .* phi;
vertices_z = [vertices,phi_array];
updated_shp = alphaShape(vertices_z);
plot(updated_shp);

Answer 1

[Matt J]

th = (pi/12:pi/12:2*pi)';
x1 = [reshape(cos(th)*(1:5), numel(cos(th)*(1:5)),1); 0];
y1 = [reshape(sin(th)*(1:5), numel(sin(th)*(1:5)),1); 0];
x = [x1; x1+15];
y = [y1; y1];
phi=3;
shp=alphaShape(x,y);

TR = alphaTriangulation(shp);
z = x*0+phi;

trisurf(TR, x,y,z);

[Annamalai Karuppiah]

Thank you!