Inaccurate Evaluation of points inside holed polygons

[michelegatto1]

Issue1.zip

I'm facing an issue trying to detect which of my query points, coming from a Digital Terrain Model, are inside the polygons of a lithological shapefile. Specifically, The issued polygon is holed and the attached image shows what happens (see lower part).

How could I solve it?

[dengwirda]

Hi @michelegatto1, I believe this is just a 'conventions' issue --- you look to be using a NaN-delimited polygon format (via MATLAB's polyshape) but inpoly is based on the more general node-edge topological layout. If you convert:

    % apparently saved in MATLAB's 'polyshape' format
    load 'Issue1/Issue1_polygon.mat'
    load 'Issue1/query_points.mat'

    % un-pack NaN-delimited polygons into topological
    % node-edge format for inpoly 
   [pp,ee] = getnan2(issue1_polygon.Vertices);
    
   [in,on] = inpoly2(query_points,pp,ee);
    
    figure;
    patch('faces',ee,'vertices',pp,'edgecolor','k','facecolor','w');
    axis equal; hold on;
    plot(query_points(in,1),query_points(in,2),'b.');
    plot(query_points(on,1),query_points(on,2),'r.');

where the getnan2 can be found here: https://github.com/dengwirda/mesh2d/blob/master/geom-util/getnan2.m. You should get the expected output:

Adding the option to convert NaN-delimited inputs automatically within inpoly seems a reasonable improvement, so I've tagged this as an option for future releases.

[michelegatto1]

It's great! Now it works fine. Thanks a lot