[filters] CropHull unexpected number of intersections

[cdel2]

Context
I am using CropHull to test if a single point is inside the hull of a sphere. In applyFilter3D(PointCloud &output) function of crop_hull.hpp, I get unexpectedly high number of intersections for the given point.

Here is what I added to the function (using this fix) :

    bool isPointInsideHull = (crossings[0]&1) + (crossings[1]&1) + (crossings[2]&1) > 1;
    if ((crop_outside_ && isPointInsideHull) || (!crop_outside_ && !isPointInsideHull)) {
      cout << "crossing ray 0 : " << crossings[0] << endl;
      cout << "crossing ray 1 : " << crossings[1] << endl;
      cout << "crossing ray 2 : " << crossings[2] << endl;

      cout << "point is inside hull !-------------------------------------------------------------- " << endl;
      this_thread::sleep_for(10000ms);
      output.push_back (input_->points[(*indices_)[index]]);
    }

Current Behavior
This is the resulting number of intersections I got for each ray :

crossing ray 0 : 1405                                                                                                   
crossing ray 1 : 1407                                                                                                   
crossing ray 2 : 1397 

Expected behavior
I expected crossings array to contain either 0 (no intersection, possibility that the point is outside), 1 (1 intersection, possibility that the point is inside) or 2 values (2 intersections, possibility that the point is outside of the sphere).

To Reproduce
I use PCL 1.8.0 on Windows 10. Here is the link to the files used :

• polygon.ply contains the hull information
• unit_test.ply is the input point cloud we want to test

@taketwo @kunaltyagi

[kunaltyagi]

There's no need to tag the maintainers on the issues.

[kunaltyagi]

As per the code, crossings[ray] is the number of polygons a particular ray from the point in question intersects.

If a ray intersects with an even number of polygons, it is outside the hull, else it is inside. I don't see where this number would be limited to 0, 1 and 2 for a concave hull. If the hull was convex, then it's a bug to have such a high number of crossings.

Could you replicate this issue using 1 point and a simple hull?

[cdel2]

The hull I made is from the point cloud of a sphere so wether it is convexe or concave has no importance here. Turned out however that I had a few self intersecting faces, which explained why I could have more than 2 intersections per point. I did the same test with a hull having no self-intersection (checking with blender that geometry is manifold). I uploaded a file convex_hull.ply which contains this hull.

I still get the following result for the same point :

crossing ray 0 : 37
crossing ray 1 : 23
crossing ray 2 : 121

[stale]

Marking this as stale due to 30 days of inactivity. It will be closed in 7 days if no further activity occurs.

[kunaltyagi]

I tried to debug the issue and came with with no sane reason why this is happening