how to find the equation for a documented curve?

hello, I' working on an experiment in bamboo and have documented a few curves that I got from my experiments. I wanted to know how i would be able to create an expression so dat I can just tweak variables in that expression to generate more curves from the documented ones in a maximum minimum range. The documented curve is a reverse curve.

I have started finding the equation by a standard quadratic equation whith 3 known points on the curve. may be it will work. Please give suggestion towards going ahead with it.

Replies to This Discussion

Permalink Reply by David Rutten on March 29, 2014 at 5:28am

Hi Nikita,

although Nurbs curves are based on polynomials, it is not particularly easy to use them to approximate f(x) = ax^N + bx^N-1 + cx^N-2+...+z equations.

Reverse curves will require at least a third power in there, so you'll need to find cubic equations at the very least. It's probably easiest to write your equations as expressions using sliders as variables:

Unless I have misunderstood the problem...

David Rutten

david@mcneel.com

Attachments:

simple_equation.gh, 4 KB

Permalink Reply by Nikita Gurav on March 29, 2014 at 5:51am

hey ...firstly,thank you for replying..

well may be u are right because the documented curves show more than 2 points controlling it (after switching the control points on), hence i think just 2degree curve wont be sufficient...im uploading the rhino file to show my documented curve so that it will be clearer.. i want to specifically have that dipping of the curve in the expression as it is specific to the material used in the actual experiment.iv used centimetres while documenting. I will look into cubic equations immediately.

thank you

Attachments:

for gh3d.3dm, 63 KB

Permalink Reply by Nikita Gurav on April 1, 2014 at 9:08pm

Hi David,

I have been able to find the equations for my documented curves using excel sheets, I'v also been able to minimise the error between the two curves as much as I can. What I wanted to know was, if I could decompose an equation into its constants and variable so that I can move head into influencing them with a certain parameter.

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