Creation of multiple arcs results in different normal vecots


Hi all, I’m trying to create an array of arcs equally spaced allong the y axis, by providing start points, end points and centre points. The planes of the arcs are all parallel to each other. However, the normal vector of these planes sometimes points to the left, and sometimes to the right, which is problematic when I try to offset the curves ( resulting to offset in the concave direction in one case, and in the convex direction in the other case). does anyone of you know what influences the normal vector of an arc’s plane ( left or right) and how to reverse it?




Hello Jesse,

That’s a really interesting observation. At first I thought it was due to the coordinates of the start point compared to the XY graph. But it seems that is not the case. Hopefully somebody more versed in Dynamo can pitch in on the matter. The only thing I can do is recommend a way to extract the offset consistently by comparing the length of the resultant arc:


Good luck!


@Dimitar @ Jesse

i had the same experience with offsetting room boundaries. 99% follow one direction 1 do not. resulting in wrong results (as in your arcs example).

maybe it were a good idea to create an issue about this inconstancy.

those are room boundaries created with an offset. as you can see thet left 2 rooms do overlap.

the e rooms on the right side behave as expected



Thanks for your help guys, and thanks for your work around Dimitar. @Peter, how do I create an issue?