rs.CurveDirectionsMatch issue

Scripting
1

Hello,

I’ve been writing a script that use python CurveDirectionsMatch function to align the curve directions and I ran into an issue - when I have co-linear lines then the above mentioned function always return true, regardless of the actual orientation…
see curves (1) on the attached picture. Find attached picture where I try to present the situation described

When the lines are not co-linear the function works as expected

I also made a test (2) : I split the smooth curve and intentionally flipped one part. function again returned true.
But when I misaligned the edges of the same curves (3) it returned false as it should

Screenshot_1
Screenshot_11211×776 38.9 KB

Is there an other way to compare curve directions without going deeper into vector math?

Only thing I have on my mind is to compare vectors at start point of each curve if it is less then 90 degrees…

BR
Aleksandar

2

Hi Aleksandre,

It is definitively a bug with Curve.DoDirectionsMatch method.

You can also use the Vector3d.IsParallelTo method with tolerance close to 90 degrees:
https://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_Geometry_Vector3d_IsParallelTo_1.htm

3

Hvala Djordje!

Thanks for the advice

I also needed a proof that I’m not overlooking something! :grinning: - because I used the DoDirectionsMatch from Rhinocommon many times before and never run into this…

I already made my own function based on calculating angle between the start point vectors that works sufficiently for me.

Thanks!
Aleksandar