Axis orientation when using Plane Normal

Grasshopper
1

Hi There,

I was trying to construct Planes using Plane Normal, which takes as input an origin point and a Z-axis. Clearly this is enough information to define a plane, but not enough to constrain the orientation of the X and Y axes in the new plane. What is it that determines these axes? I am getting them coming out irregularly, although clearly with some pattern to it.

The attached file has a circle of origin points, with vectors to define my Z-axis. Deconstructing the plane and displaying the X-axis of each shows my issue. What is the rule here?

VectorPlaneNormal.gh (8.7 KB)

Canvas at 20;32;35
Canvas at 20;32;351115×896 68.3 KB

2

I don’t know the “rule” (maybe GH takes its best guess…) but you could use Align Plane to orient them all in the same direction.

Canvas at 00;38;10
Canvas at 00;38;101146×793 427 KB

Or,
you can create your own normal planes using Cross Product and Construct Plane – probably more predictable.

VectorPlaneNormal-b.gh (14.8 KB)

Canvas at 01;02;46
Canvas at 01;02;461146×793 82.7 KB

You’ll notice that the two results are not the same, perhaps because the circle is off-center.

3

Thank you very much! Both of these look to be good ways to regain consistency, and I will use them for the project I was working on… but I am still bemused by the actual behaviour.

Best wishes,

Bob