Cut out a cuboid out of a bigger cuboid and calculate the resulting coordinates

Question

Nicolas Kaiser 2023-3-22

0
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https://ww2.mathworks.cn/matlabcentral/answers/1933215-cut-out-a-cuboid-out-of-a-bigger-cuboid-and-calculate-the-resulting-coordinates

评论： Nicolas Kaiser 2023-3-31

Hi community,

I describe multiple cuboid objects with alphashape. Now i want to cut out a smaller cuboid out of a bigger cuboid and get the remaining coordinates of the big cuboid.

Is there any easier solution to do so? Like simular to the polyshape function 'subtract' (https://de.mathworks.com/help/matlab/ref/polyshape.subtract.html). I tried it also ones with the polyshape function. For this i used the top of the bigger cuboid and the top of the smaler cubiod, so two 2D-areas, and used the subtract function for polyshape'. Afterwards i repmat the coordinates and added the max and min corresponding z-coordinate. The code:

coordinates_bigCubiod = [-100 -100 -50; -100 -100 50; 100 -100 50; 100 -100 -50;...

100 100 -50; -100 100 -50; -100 100 50; 100 100 50];

coordinates_smallCubiod = [-25 -12.5 -25; -25 -12.5 25; 25 -12.5 25; 25 -12.5 -25;...

25 12.5 -25; -25 12.5 -25; -25 12.5 25; 25 12.5 25];

polyshape_bigCubiod = polyshape(coordinates_bigCubiod([2 7 8 3],[1 2]));

polyshape_smallCubiod = polyshape(coordinates_smallCubiod([2 7 8 3],[1 2]));

%substract cuboid

polyshape_bigCubiod = subtract(polyshape_bigCubiod,polyshape_smallCubiod);

vertices_topPlate = polyshape_bigCubiod.Vertices(~logical(sum(isnan(polyshape_bigCubiod.Vertices),2)),:);

z_values = unique(coordinates_bigCubiod(:,3));

z_values = repelem(z_values,size(vertices_topPlate,1));

coordinates_bigCubiod = [repmat(vertices_topPlate,[2,1]) z_values];