# Filling area between two planes in 3d plot

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Colby on 1 Sep 2015
Commented: Ksenia Shukhin on 31 May 2022
I'm trying to more or less plot an amorphous blob on a 3d plot. I know the top, and I know the bottom. Is there an easy way to fill the space between? For example, if I have
surf(peaks)
hold on
surf(peaks + 5)
hold off
How could I connect the two planes so it's like a volume?
Thank you so much for your time

Mike Garrity on 4 Sep 2015
The isosurface approach that Tim suggested is possible. Here's an example of how you'd do that. It's a bit involved and it uses quite a bit of memory:
nx = 25;
ny = 25;
nz = 25;
[x,y] = meshgrid(linspace(-2,2,nx),linspace(-2,2,ny));
z1 = peaks(x,y);
z2 = peaks(x,y) + 5;
surf(x,y,z1);
hold on
surf(x,y,z2)
%%Create 3D grid containing distance to closest surface
[y3,x3,z3] = ndgrid(linspace(-2,2,ny),linspace(-2,2,nx),linspace(-10,15,nz));
v = zeros(size(z3));
for r=1:ny
for c=1:nx
for s=1:nz
d1 = z3(r,c,s) - z1(r,c);
d2 = z2(r,c) - z3(r,c,s);
if d1 < 0
v3(r,c,s) = d1;
elseif d2 < 0
v3(r,c,s) = d2;
else
v3(r,c,s) = min(d1,d2);
end
end
end
end
%%Create isosurface
figure
p = [patch(isosurface(x3,y3,z3,v3,0)), ...
patch(isocaps(x3,y3,z3,v3,0))];
isonormals(x3,y3,z3,v3,p(1))
set(p,'FaceColor','yellow')
set(p,'EdgeColor','none')
set(p,'FaceLighting','gouraud')
view(3)
camlight right
You need both isosurface and isocaps there. The isosurface command creates the parts inside the volume (the same parts surf created) while isocaps creates the parts along the boundary. You can also combine isocaps from that example with your surface objects like this:
figure
surf(x,y,z1);
hold on
surf(x,y,z2)
isocaps(x3,y3,z3,v3,0);
Ksenia Shukhin on 31 May 2022
Hi Mike!
I have used your code for creation a 3d object, thank you a lot. But now the question is how to create stl file from this. Maybe you can help?

Tim Jackman on 3 Sep 2015
One option would be to create an isosurface, but to do that you would need to convert your data into a 3-D gridded data. This link has some more information and a couple examples to follow:
Based on the example you provided, and quick way to fill the space in between the two surfaces would be to apply a patch. For example:
surf(peaks)
hold on
surf(peaks + 5)
hold off
Now place a polygon along one edge by supplying the X, Y, and Z coordinates along with the color you want:
patch([1;1;49;49],[1;1;1;1],[0;5;5;0],[1,0,0])

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