Find all neighbors near the specified Point(x,y,z,) in 3D matrix

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Erfaneh 2014-9-12

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https://ww2.mathworks.cn/matlabcentral/answers/154490-find-all-neighbors-near-the-specified-point-x-y-z-in-3d-matrix

评论： Image Analyst 2017-10-7

I want to find all neighbors who are near the specified point(x,y,z) or find all objects who are in k distance from specified point(x,y,z).

For example I want to find all objects near the point(1,1,1) or they are in k distance from point(1,1,1).

I try to use from rangesearch function, but I can't use it.

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Walter Roberson 2017-10-6

Unless the point cloud has special properties, the 27 nearest neighbours will include points that are not at "adjacent" coordinates. Do you have reason to expect that the points will form a cubic grid that is aligned with the axes? If so then the problem reduces to one of examining the min() and max() of the coordinates to figure out where the ranges begin and end, and determine the coordinate spacing, after which everything else is pre-determined by the properties of a cuboid with appropriate size.

Image Analyst 2017-10-7

在 MATLAB Online 中打开

You could also use meshgrid() to create a list of coordinates:

middleRow = 100; % Whatever - wherever it is for this cube.
middleCol = 1000; % Whatever - wherever it is for this cube.
middlePlane = 10; % Whatever - wherever it is for this cube.
[rows, columns, planes] = meshgrid(1:3, 1:3, 1:3)
% Make 1-D arrays
rows = rows(:) + middleRow
columns = columns(:) + middleCol
planes = planes(:) + middlePlane
% Get rid of center voxel so we have only neighbors
rows(14) = []; % Delete middle one
columns(14) = []; % Delete middle one
planes(14) = []; % Delete middle one

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采纳的回答

Image Analyst 2014-9-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/154490-find-all-neighbors-near-the-specified-point-x-y-z-in-3d-matrix#answer_151553

在 MATLAB Online 中打开

See the FAQ on how to make a sphere: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F

Then just mask the array

withinSphere = array3D .* sphereVoxels; % Voxel values.

After that I don't know what you want because all you say is you want to "detect all objects" but "detect" is such a vague, imprecise term that I don't know what sort of numerical data to return to you. Please define "detect".