# Worksheet Data

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I posted this inquiry in the General Discussions Forum, but that may not have been the best choice.

So....perhaps directing this to Julian Carr or Pat Stanford,  the smartest guys in the room, you guys may have some ideas?

Without getting into a lot of explanation, I am working on a Project that has a very organic domed ceiling. (Note the attachment) Presently it is made up of several nurbs surfaces.  What I was HOPING to do is to create a worksheet that can describe the curved nurbs geometry for each of the edges of the shape. In reality, I only need data for 1/2 of the object since it can be mirrored. So, the data I was wanting to obtain would include, typically, the radii of the curves, lengths of the segments, etc. I tried messing with this a bit by extracting the edges from the nurbs surfaces, which worked splendidly, and the data in the OIP for each nurbs curve sort of arcanely explained each nurb, but produced no curve data. Anyway....this is way above my pay grade, and it may not be possible to get this information into a worksheet  but I thought I would put it out there if you guys have any feedback on it.

Thanks

-Kev

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NURBS curves don't have radii — unless they describe circles. You can extract coordinates, and increasing the degree of the curve will give you more points.

NURBS are described by a polynomial equation, with the degree of the NURBS curb describing the degree of the equation. For example, a 3rd degree curve is described by y = aX3+bx2+xc+d. The NURBS curve is divided into pieces, with each piece having a different equation. (And that's a bit of an oversimplification)

What's your ultimate goal for the data? (I imagine as a construction aid) Depending on your final tolerance, your easiest approach is going to be a series of XYZ coordinates for either the surface or extracted curve.

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JB

Thanks for responding.

I love math, but never even considered the fact that nurbs are sort of their own animal.

I do appreciate your mini math lesson and explanation. You are definitely in a different league than I, and it is

obvious you had probably been hangin out with Stephen Hawking 🙂

Yes, all this does relate to a construction Project. My associate and I are working with someone who is going to fabricate this

ceiling dome. No doubt sending the data to a CNC machine, I imagine.  I am not directly in the loop so I do not have all the details and have not actually communicated with this person. I am mainly in charge of doing the 3d modeling, renderings and presentational graphics  for the Project.

We will be relying on this person to make sure he builds the ceiling dome with accuracy, as intended. So....we ( I) was hoping to create a worksheet or document that could describe and define the data for all the nurbs curves, etc. and send that info to the fabricator to verify we are all on the same page.

There ya have it. I was racking my tiny brain as to how to best procure all this, which is why I was considering the potential use of a worksheet to do so. I am certainly open to any other thoughts.

Thanks again

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I would consider creating a series of parallel profiles each of which can be CNC'd in 2d to form a 3d buck.

Shift-H to Create Contours (profiles)

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You could also export the file as a vectorscript text file. This will show how vectorworks creates the nurbs curves as a script. It is very accurate for simple geometry but it tends to skip objects with more complicated geometry.

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Thanks guys for the suggestions. I will look into them.

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