represent a volume given two surfaces
显示 更早的评论
I have two surfaces given by the grids X, Y, Z1 and X, Y, Z2. Both Z grids share the same X and Y grids. I can plot each Z surface, but I'd like to represent the space between them as a solid mass. Is there a way to represent the space between these two Z surfaces a simple volume akin to a patch or a fill in 2D space?
4 个评论
Walter Roberson
2013-8-9
Do you just need the outside "skin" drawn; or do you need the inside drawn as long blocks with rectangular cross-section; or do you want the inside filled with a bunch of cubes of uniform size ?
Chad Greene
2013-8-9
Walter Roberson
2013-8-9
Any NaN or inf values? If not then the skin to be drawn would just be based on the rectangle around the X and Y limits, at least if the grids are regular spacing. Are the X Y arrays perhaps not regular spacing ?
Chad Greene
2013-8-9
采纳的回答
Saturday EDIT: I took 5 minutes to build an example closer to your case; see the new section after my initial answer.
=== Initial answer.
The issue is to locate the boundary. Once you have it, it's easy: here is an example assuming that the boundary is known (cylinder with octagonal base):
% - Define (x,y) base and z for the example.
Xbnd = [2 1.41 0 -1.41 -2 -1.41 0 1.41 2].' ;
Ybnd = [0 1.41 2 1.41 0 -1.41 -2 -1.41 0].' ;
Z1bnd = rand(size(Xbnd)) ; Z1bnd(end) = Z1bnd(1) ;
Z2bnd = 1 + rand(size(Xbnd)) ; Z2bnd(end) = Z2bnd(1) ;
% - Define patches nodes (from now on, it is no more specific to the example).
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') ;
rotate3d ; % Enable 3D rotations with the mouse
% in the figure.
As you are dealing with a grid (even if nodes are irregularly spaced, as it doesn't alter the topology), one option for determining the boundary is to work with the image processing toolbox on a BW image generated with ~isnan(Z). Once you get row/col IDs of pixels of the boundary using BWBOUNDARIES [ 1, 2 ], you can use them to select corresponding elements in X, Y, Z1, and Z2.
So you could start trying doing something like (assuming that the nan values are in Z1 and/or Z2):
BW = ~(isnan(Z1) | isnan(Z2)) ;
BW_filled = imfill(BW, 'holes') ;
boundaries = bwboundaries(BW_filled) ;
then maybe filter out unwanted boundaries, or keep the longest one. Finally, you would have something like
Xbnd = X(sub2ind(size(X), boundary(:,1), boundary(:,2))) ;
Ybnd = Y(sub2ind(size(Y), boundary(:,1), boundary(:,2))) ;
where boundary equals boundaries{k} for k the index of the longest boundary, or for all k if you iterate over boundaries.
=== Example closer to your case.
close all ; clear all ; clc ;
% - Build demo X, Y, Z1, Z2.
[X, Y] = meshgrid(1:10, 1:10) ;
X = X + rand(10) - 0.5 ;
Y = Y + rand(10) - 0.5 ;
Z1 = sin(X) .* cos(Y) ;
Z2 = X + Y.^2/10 ;
idNaN = (X-5).^2 + (Y-5).^2 > 3^2 ; % Set Z1 to NaN around approx.
Z1(idNaN) = NaN ; % disk shape.
% - Get boundary.
BW = ~(isnan(Z1) | isnan(Z2)) ;
BW_filled = imfill(BW, 'holes') ;
boundaries = bwboundaries(BW_filled) ;
boundary = boundaries{1} ; % Only 1 boundary in this trivial example.
% - 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') ;
rotate3d ; % Enable 3D rotations with the mouse
% in the figure.
3 个评论
Chad Greene
2013-8-12
Pooyan
2023-9-11
dear cedric...is there any code to fill whole between two surface and build a 3d shape...i mean not a hollow shape...i want to do this...
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Surface and Mesh Plots 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
