Has MATLAB implemented a polygon offset function?

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Stephanie Farney 2021-1-8

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https://ww2.mathworks.cn/matlabcentral/answers/712253-has-matlab-implemented-a-polygon-offset-function

评论： Steven Lord 2021-1-13

Hi! I have 2D CMM data mapping the inside of a pipe at a plane of interest prior to coating and coating thickness measurements at various points inside the pipe. I want to plot the CMM data, offset each wall of the pipe by its corresponding thickness, and use the offset data to calculate the coated cross-sectional area of the pipe (see diagram below). Is there a simple way to do this? If not, does MATLAB have a built-in function to offset the data by a uniform thickness (similarly to CAD software)?

Thanks!

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Answer 1

Matt J 2021-1-8

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https://ww2.mathworks.cn/matlabcentral/answers/712253-has-matlab-implemented-a-polygon-offset-function#answer_593963

编辑：Matt J 2021-1-8

Sounds like you could do that with polybuffer

https://www.mathworks.com/help/matlab/ref/polyshape.polybuffer.html

and polyshape.area()

https://www.mathworks.com/help/matlab/ref/polyshape.area.html

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Stephanie Farney 2021-1-13

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Thank you, that got me on the right track. However, I'm still unable to offset the data by a uniform amount. If it helps, my code resembles the following:

bound = boundary(data.X,data.Y);
contour = polyshape(data.X(bound),data.Y(bound));
coatedContour = polybuffer(contour,avgThickness); 

When I plot contour and coatContour, the coating thickness on the top and bottom walls is significantly thicker than the coating on the side walls. As a note, using the boundary gets me an area that better matches the uncoated area calculated by the supplier, but I still have the same problem when I exclude it.

Do you know what might cause this issue?

Thanks again!

Steven Lord 2021-1-13

Can you share a small sample of data with which you can reproduce this behavior? Please include either a data set that's small enough to include as text in a comment or a small MAT-file as an attachment to a comment.

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