Bug? "Perpendicular frame could not be solved"

Grasshopper
1

Perpendicular frame could not be solved.gh (6.9 KB)
I am using R8 SR13 on Windows 11.

image
image1669×888 88.5 KB

2

I baked the arc, moved the middle control point away and back and then it works. Weird.

3

Perpendicular frame_2024Dec1a
Perpendicular frame_2024Dec1a962×325 27.6 KB

Perpendicular frame_2024Dec1a.gh (4.6 KB)

4

Perpendicular_frame_script_cs.gh (9.7 KB)

Evaluating the curve with rhinocommon works…
the attached script does the job.
so maybe it is a bug ?

    private void RunScript(Curve crv, double t, ref object a)
    {
        Point3d ptt = crv.PointAt(t);
        Vector3d vt, vn, vy;
        vt = crv.TangentAt(t);
        vn = crv.CurvatureAt(t);
        if (vn.IsTiny())
        {
            a = Plane.CreateFromNormal(ptt,vt);
        } else
        {
            vt.Unitize();
            vn.Unitize();
            vy = Vector3d.CrossProduct(vt,vn);
            a = new Plane(ptt,vn,vy);
        }
    }

maybe the gh component does handle some special cases - but does to much safety and fails ?

EDIT:
…also rotating the curve by 45 degree (but not 1 degree) will result in a correct perpendicular frames from the component…

5

Is this a bug?