void ovd::VoronoiDiagram::add_edges(ovd::HEFace, ovd::HEFace, ovd::HEFace, std::pair<void*, void*>): Assertion `(new_count % 2) == 0' failed. Aborted (core dumped)

[zengtaiping]

When I am trying to use the cpp_examples medial_axis, I found the error:

void ovd::VoronoiDiagram::add_edges(ovd::HEFace, ovd::HEFace, ovd::HEFace, std::pair<void*, void*>): Assertion `(new_count % 2) == 0' failed.

With the code:

    ovd::Point p0(3.25,1.15);
    ovd::Point p1(1.1,1.15);
    ovd::Point p2(-0.275,1.15);
    ovd::Point p3(-1.25,0.475);
    ovd::Point p4(-0.95,-1.1);
    ovd::Point p5(1.1,-1.15);

    int id0 = vd->insert_point_site(p0);
    int id1 = vd->insert_point_site(p1);
    int id2 = vd->insert_point_site(p2);
    int id3 = vd->insert_point_site(p3);
    int id4 = vd->insert_point_site(p4);
    int id5 = vd->insert_point_site(p5);

    vd->insert_line_site(id0, id1);
    vd->insert_line_site(id1, id2);
    vd->insert_line_site(id2, id3);
    vd->insert_line_site(id3, id4);
    vd->insert_line_site(id4, id5);
    vd->insert_line_site(id5, id0);
    vd->check();

However, when I remove Point p1 and remake, it works without errors.
With the code:

    ovd::Point p0(3.25,1.15);
    // ovd::Point p1(1.1,1.15);
    ovd::Point p2(-0.275,1.15);
    ovd::Point p3(-1.25,0.475);
    ovd::Point p4(-0.95,-1.1);
    ovd::Point p5(1.1,-1.15);

    int id0 = vd->insert_point_site(p0);
    // int id1 = vd->insert_point_site(p1);
    int id2 = vd->insert_point_site(p2);
    int id3 = vd->insert_point_site(p3);
    int id4 = vd->insert_point_site(p4);
    int id5 = vd->insert_point_site(p5);

    vd->insert_line_site(id0, id2);
    // vd->insert_line_site(id1, id2);
    vd->insert_line_site(id2, id3);
    vd->insert_line_site(id3, id4);
    vd->insert_line_site(id4, id5);
    vd->insert_line_site(id5, id0);
    vd->check();

I think the different points caused the problems. But I did not find why it happens.
Thanks.

[aewallin]

can you draw your points and line-sites in a 2D drawing and attach it here?
(for example crossing lines are not allowed input to openvoronoi)

[zengtaiping]

@aewallin Thanks for your quick response.
There are no crossing lines in this simple example.
I plot the points and connected lines without the last point to the start point, for easy viewing.
The six points figure with error:

The five points figure without error:

[zengtaiping]

Any suggestions to solve this problem? @aewallin

[aewallin]

in your first example above, I am guessing the error comes from inserting the second line-site, vd->insert_line_site(id1, id2), which is co-linear with the first site?

one would have to study the code in depth to look at what is causing the problem. line-sites that are either at 90-degrees to each other, or like in your case at 0-degrees/co-linear to each other are special cases.

[yuyue2013]

So line-sites can not at 90-degrees to each other?

[aewallin]

There are two ways to solve this:

• make the generic code that handles any site-insertions robust enough so it handles everything well enough. This needs a definition of 'well enough' e.g. based on topology or numerical precision.
• try to write special functions for each special case.

In practice I haven't had much time to work on openvoronoi in the past years, so I don't know if/when this might move forward. If there's another maintainer that is eager to take over then please go ahead!

[dbdxnuliba]

hello @zengtaiping , did you find the solution