Elegant method, perp line

Can someone help with the best way to draw a line perpendicular to the line just drawn and from the last point

In 2D? A simple way (simple is good) would be to continue in the same direction and then turn the line by 90 degrees. Or construct it with the vector end-start transformed by (-y, x, 0) (counterclockwise) or (y, -x, 0) (clockwise).
In 3D? You can use the cross product with the vector that forms the base plane.

I hope this helps,


Giulio Piacentino
for Robert McNeel & Associates