line perpendicular to a surface

Hello, I am in need of help. How can I go about to creating a line that is perpendicular to a surface i.e I have a pyramid and I want to create a line that is perpendicular to one of its faces at its center so that I can create another pyramid at that face such as in the image. I am able to do it in regular rhino by orient camera to surface then make2d then rotate3d back into its spot; however my outcome would be much faster if I can figure out a way to do this in grasshopper since each initial "host" pyramid is derived from a Delaunay equation and I plan on using the Delaunay lines as the generators of my pyramids.

Outcome picture attached is what I'm trying to achieve through grasshopper

Thanks

Cesar Beltran

Attachments:

Pyramind_Perpendicular_to_face.3dm, 78 KB
Pyramind_Perpendicular_to_face_outcome.JPG, 310 KB

Replies to This Discussion

Permalink Reply by Michael Pryor on September 22, 2011 at 2:21pm

I have U&V for surface frames both set to 1

Permalink Reply by cesar on September 22, 2011 at 2:45pm

Miachel thanks for helping me out however I cant seem to get the flattened faces to work correctly

Permalink Reply by Michael Pryor on September 22, 2011 at 2:55pm

but your f output for surface frames is not flattened in your screenshot, it should be flattened.

Permalink Reply by cesar on September 22, 2011 at 3:01pm

I flattened it but it still gives me multiple lines to each point and theyre not going perpendicular to its corresponding face

Permalink Reply by Michael Pryor on September 22, 2011 at 3:23pm

It is because of the way you built the geometry in rhino (it matters) sure all the triangles are joined as one brep but as surfaces they all have different normals, essentially because they started as different shapes. Try this way, it goes face by face, you just have to change whether the length is a positive or negative number based on that surfaces normal. I'm sure someone else knows a better way but here is this for now.

Permalink Reply by cesar on September 22, 2011 at 3:36pm

thanks this one worked better only thing I'm dreading is having to do it for all my pyramids and its faces

Permalink Reply by Michael Pryor on September 22, 2011 at 3:39pm

its ok, If your pyramids are neatly constructed then this should work (I put more thought into it, sometimes I forget some components exist) The part highlighted purple reverses the normals if they are going the wrong way, you may or may not need it depending on the surface. In this case i needed it.

Permalink Reply by Pieter Segeren on September 22, 2011 at 4:36pm

If I understand the question right...

Permalink Reply by Michael Pryor on September 22, 2011 at 4:41pm

whats the last component?

Permalink Reply by Pieter Segeren on September 22, 2011 at 4:48pm

Extr (Extrude Point) (in Surface > Freeform)

Permalink Reply by Michael Pryor on September 22, 2011 at 4:51pm

interesting, is there any difference in my method compared to yours, out of curiosity, maybe in computational time, or is one more full-proof? It interests me how many ways others do tasks.

Permalink Reply by Pieter Segeren on September 22, 2011 at 5:14pm

must be a million ways ;) I just made this hoping I understood the question right. Since I only needed the normal, I left the uv(w) to a sort of default 0,0,0.

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