# Slide vertices based on angle of adjacent edges

I want to extrude a boundary edge such that angles between any given newly generated perpendicular edge and the edges on either side are equal. That is, I want to do this:

The gif was accomplished by first extruding in the Z axis and then fattening with ⎇ AltS:

Is there a way to do this without the intermediate step? When I do ⎇ AltS with just a boundary edge I get this odd behavior (seems the normals are just set arbitrarily?)

• I may have got your meaning wrong .. but the 'Offset Edges' Add-On > Extrude preserves angles as you describe .. each new edge from a vertex bisects the angle between the edges which previously met at that vertex. However, unlike your illustration, not all the generated bisectors are the same length. Is that important? – Robin Betts Jul 9 '18 at 8:08
• Would call that a miter extrude Somewhat related particularly the ammended script here Which use the miter points via method outlined here mehods here to stroke edge mesh in XY plane. – batFINGER Jul 9 '18 at 9:18
• @RobinBetts I would actually prefer that the new boundary edges be parallel to the old ones, as that addon does. So that would be perfect, but for the lack of fast tweakability. Though an edge slide can tweak it once the geometry exists, so I'll accept it :) – gandalf3 Jul 9 '18 at 21:19
• @batFINGER That does seem rather like what I'm after, but it seems that at least the OSM version does some kind of beveling as well? – gandalf3 Jul 9 '18 at 21:20
• Second creates new mesh without centre line., and miters bends ( has some edge cases to fix or it twists. ) Believe what you are after is: Project edges onto view plane, calculate miter vectors and extrude... what do you think? – batFINGER Jul 10 '18 at 13:21