How do I graph and calculate the volume between two surfaces?

I have 3d coordinates in the minus region (known x,y,z) a flat surface in the +ve matching the x,y coordinates and I want to make a volume between these 2 surfaces and calculate it as well.

Thanks! I can plot both surfaces just fine I need help connecting them:

Here is part of my code:

xv = linspace(min(x), max(x), nx);
yv = linspace(min(y), max(y), ny);
[X,Y] = meshgrid(xv, yv);
Z1 = griddata(x,y,z1,X,Y);
Z2 = griddata(x,y,z2,X,Y);

surf(X, Y, Z1); 
hold on;
surf(X, Y, Z2);

Answer 1

[Ayush Gupta]

The issue is to locate the boundary. Once you have it, it's easy: here is an example continuing your code assuming that the boundary is known (cylinder with octagonal base)

% Getting boundary. 

bw = ~(isnan(z1) | isnan(z2)); 

bw_flled = imfill(bw,'holes'); 

boundaries = bwboundaries(bw_flled) ; 

boundary = boundaries{1} ;              

  

% - Define x,y,z1,z2 values on the boundary. 

Xbnd  = x(sub2ind(size(x), boundary(:,1), boundary(:,2))) ; 

Ybnd  = y(sub2ind(size(y), boundary(:,1), boundary(:,2))) ; 

Z1bnd = z1(sub2ind(size(z1), boundary(:,1), boundary(:,2))) ; 

Z2bnd = z2(sub2ind(size(z2), boundary(:,1), boundary(:,2))) ; 

  

  % - Define patches nodes. 

Xdata = [Xbnd(1:end-1), Xbnd(2:end), Xbnd(2:end), Xbnd(1:end-1)].' ; 

Ydata = [Ybnd(1:end-1), Ybnd(2:end), Ybnd(2:end), Ybnd(1:end-1)].' ; 

Zdata = [Z1bnd(1:end-1), Z1bnd(2:end), Z2bnd(2:end), Z2bnd(1:end-1)].' ; 

  

  % - Plot patches. 

patch(Xdata, Ydata, Zdata, 'm') ; 
%Enable 3D rotations with the mouse in the figure. 
rotate3d ;