reparametricizing a bezier curve

Replies to This Discussion

Permalink Reply by Damien Alomar on May 26, 2009 at 11:19pm

Reparameterizing simply sets the beginning and ending parameter at 0 and 1, respectively. Parameters along a curve are not the same as the length along a curve. In other words, evenly spaced parameters along a curve may not actually equate to those parameters being the same distance away from each other or equidistant along a curve.

As to Beziers vs NURBS, I'm really not sure, but I would imagine that their parameterization would not be incredibly different. In the simple case of the bezier span that can be created in GH (minus scripting of course), it really doesn't make that much of a difference at all.

-Damien

Permalink Reply by David Rutten on May 27, 2009 at 12:54am

Beziers are a subset of Nurbs curves. In fact, even though OpenNurbs supports bezier curves and patches, the Bezier component simply makes a nurbs curve that looks like a bezier span.

Permalink Reply by Damien Alomar on May 27, 2009 at 9:12am

Thanks for the clarification on that David. I figured that Rhino (more or less) created nurbs representations of those other curve types (Bezier, Polynomials)

Permalink Reply by Dimosthenis Stogios on May 27, 2009 at 4:33am

Hi Gabriel... may I ask how did you reparameterise the curve, because I can not find a component inside Grasshopper?
As you are suspecting, indeed Beziers do not have a parameter range, the knot vector nurbs do have, so there is not such thing as reparameterision for them. But as David Rutten says, in a Nurbs environment, such as Rhino, the Beziers are represented thru their nurbs superset so they do in fact have a parameter range. in the case of, say, a curve of degree 3 with 4 control points, this range would be something like 0,0,0,1,1,1; if it was like 0,0,0,2.45,2.45,2.45, reparameterisation would simply turn the 2.45s to 1s, and the curve would stay still the same. As your question implies though, there may be a chance that the algorithm you have used has converted the parameters of your curve to some other way...

Permalink Reply by David Rutten on May 27, 2009 at 4:40am

The curve parameter object itself has an option to Reparameterize all curves that pass through it.
Also see the help topic for the Curve Parameter.

Permalink Reply by Akira on April 8, 2011 at 5:41am

Hi David,

 

I have a Problem. I want to reparametrization some curves.

where can I find this Information "Curve Parameter" with Grasshopper?.

 

 

Thank you

Juanma

 

 

Permalink Reply by Danny Boyes on April 8, 2011 at 5:48am

The Curve Param is on the first Tab "Param" and is in the first Section "Geometry" it has a spiral icon. But times have moved on since 2009 and every input that can take curves or surfaces has a Reparameterize option on the context menu accessed by right clicking the input.

Permalink Reply by Akira on April 8, 2011 at 6:08am

Thank you very much!!!

 

take care

juanma

Permalink Reply by Akira on April 8, 2011 at 6:15am

...have I any control about the Reparametrize option?? equidistant?

Thanks

Permalink Reply by David Rutten on April 8, 2011 at 7:44am

Hi Akira,

 

nope. Equidistant has nothing to do with parameterization. The only thing that changes is the domain of a curve, not the shape, the locations of the control-points, the degree or anything else. Although it is technically possible to assign any non-zero domain to any curve, Reparameterize always sets the domain to {0;1}

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Akira on April 8, 2011 at 7:57am

Thank you again. Sorry, I would to say the position of control points (equidistant).

 

Juanma

 

 

Permalink Reply by Danny Boyes on April 8, 2011 at 8:22am

That would be a different curve. You could try Rebuild Component Curve Tab> Util Section> Rebuild