MATLAB Answers


How can I extract the slices of a 3D matrix in x-direction from a 3D matrix?

Asked by Javad
on 6 Jul 2018
Latest activity Commented on by Javad
on 12 Jul 2018
I have a 3D matrix, which is a model of the porous media of a rock. I want to extract three 3D matrices from it so that each contains the 2D slices in a specific direction, for example x. To be clear, the matrix x contains the 2D slices in x direction, y in y-direction and z in the z-direction. I appreciate any hint or help to solve my issue.


It is unclear what you want. The original 3D matrix already has 2D slices in each direction that you can get at with indexing. E.g.,
xyz = original 3D matrix
k = whatever
xyz(k,:,:) --> k'th slice along x direction
xyz(:,k,:) --> k'th slice along y direction
xyz(:,:,k) --> k'th slice along z direction
Do you mean you want to permute the data so the slices are always in the first two dimensions? Or ...?
Dear James First, thanks for your answer. But I think my question was not clear. To be clear I explain more. I have 3D matrix, which is in fact a digital rock model. All the arrays of the matrix are 0 or 1. I want to draw the streamlines in it using the command 'streamline'. But this command need x, y, z. I want to extract these three matrices from my 3D matrix. Can you help me in this regard? Thanks

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1 Answer

Answer by Anton Semechko on 6 Jul 2018
 Accepted Answer

Suppose you have G, which is a Y-by-X-by-Z 3D array, then
i-th xy slice:
G_yx=G(:,:,i); % Y-by-X array
i-th xz slice:
G_xz=permute(G(i,:,:),[2 3 1]); % X-by-Z array
i-th yz slice:
G_yz=permute(G(:,i,:),[1 3 2]); % Y-by-Z array

The above link explain it. Also, you can load it using 'load wind'. I look forward to hearing from you. Many thanks
I see. Let's say G is your Ny-by-Nx-by-Nz 3D image and [dx,dy,dz] are dimensions of a single voxel. To get get (x,y,z) coordinates of the voxels do:
The variables 'x', 'y', and 'z' have the same dimensions as G, and can be used as input to the 'isosurface' function along with G to extract a triangular mesh of the level-set surface G==1.
Dear Anton
Many thanks. It works

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