# How to extrude a polysurface in a certain direction from the origin

Hi guys. I’m a newbie.
What I’m most curious about is how to extrude a polysurface in a certain direction from the origin. The problem is that I’m so new… I don’t know where to start.
Please recommend a solution to this question and a Wepsite or YouTube site for reference!
even a little advice can be of great help. very appreciative!

“extrude in a certain direction”
ok, sure:

“extrude in a certain direction from the origin
… what do you mean with that?

In grasshopper geometries are always absolute. Vector too.
You can construct or orient a geometry in a plane (like CPlane in rhino) but the result is directly written in absolute coordinate again.

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Actually, what I want to implement is to put a frame at the bottom of each visible staircase. like this.

However, since the shapes of the stairs are all different, I would like to use Grasshopper.
So, I first created edge lines for each step and joined these lines.
(when i offset without joining, the offset lines will be offset outward.)
i want to offset the line inward by the thickness of the second frame and create a frame along that line.

This is the rough shape I created, but the shape, position, and size of the frame are not consistent.

hey, giving the “offset” plane input a “xy plane” sometimes solve this issuee otherwise please rigth click the containers → internalise data and upload the gh file

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If I understood what you are asking for:

There are many ways to do that, for my knowledge using loft from two curves is the easiest to write and pretty optimal calculation time. Although, you could use number of other methods to do that like: “Boolean Difference” which is “Solid Difference” equivalent in Grasshopper, and then do extrusion to a Z direction etc…

Hope it helps
Grasshopper Steps frame.gh (13.2 KB)

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