Questions on the spline-related functions of Mathematica (BezierCurve[], BSplineCurve[], etc.).

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8
votes
4answers
353 views

BSplineFunction derivatives wrong if using weights?

In my work, I make heavy use of non-uniform rational B-spline (NURBS) functions, defined using the function BSplineFunction with the option defining ...
13
votes
4answers
1k views

Implementation of smoothing splines function

I have some problems in writing a module for spline smoothing. Actually, I have been trying for about two weeks. My listing is here: ...
11
votes
1answer
188 views

How to specify PDE Boundary condition on Bspline?

Context I would like to solve a PDE on a boundary which is parametrized as a BSpline. I am trying to solve the force-free Grad-Shafranov equation on a ...
1
vote
1answer
103 views

Interpolation of a NURBS curve

Known that NQ=P where N is the Bspline basis function, Q is the control point that we wish to locate, P is the data points given ( the curve must pass through it) is there any way to modify the "N" ...
1
vote
2answers
301 views

How to know form of plotted Bézier function

Simple scenario is to see the Bézier function, but how to know which polynomial approximate it? ...
13
votes
2answers
153 views

Is there a way to get BSplineFunction beyond MachinePrecision?

I have been using BSplineFunction (Mathematica 8) to generate a smooth representation of some data, which I might then do some further processing on. As I ...
21
votes
4answers
563 views

Arbitrary precision spline interpolation

The current implementation of Interpolation does not allow arbitrary precision spline interpolation. Yu-Sung Chang says here that "it is not hard to implement it ...
4
votes
1answer
70 views

What's the difference between Interpolation[pts, Method -> Spline] and BSplineCurve?

Last month, I answered a question about spline interpolation,please see here Now I do the following operations ...
0
votes
0answers
37 views

3D interpolation [duplicate]

I have four column data with first 3 column denoting x,y,z and fourth column energy. x variable is actually angle. Now I want to interpolate over all three indepdent variable (x,y.z) with ...
3
votes
1answer
173 views

Understanding polyharmonic splines

Rahul Narain and J.M. gives implementation of the thin plate polyharmonic splines in this post. Rahul Narain's method is clear. J.M.'s is convenient to reuse. But J.M. used too many ...
2
votes
1answer
115 views

Failed to create a special random-disturbed initial condition for partial differential equation

I try to use BSplineFunction to creat a initial condition for NDSolve which has periodic boundary condition, that is realized by ...
4
votes
0answers
59 views

Multidimensional arbitrary precision spline interpolation on the grid

This question is a generalization of the previous one for multiple dimensions. In the answer to that question an implementation for the clamped spline interpolation for 1D case and arbitrary degree of ...
2
votes
1answer
159 views

Confusion with SplineFit (Angle calculation)

This question is continuation to this other one I am creating polymers (where each monomer is of equal length) using this method: ...
2
votes
1answer
63 views

Why are these methods giving me different results? (Trying to test SplineFit)

I am creating a polymer(where each monomer is of equal length) using this method: ...
2
votes
1answer
89 views

How to find if x-y point falls within a closed BSplineCurve

Here's a simple Manipulate with a closed BSplineCurve, and a Locator. ...
14
votes
2answers
176 views

Color Blend in BezierCurve

How can I color a BezierCurve from Red into Green just as ...
10
votes
1answer
227 views

How can I make FilledCurve smoother?

In How can I generate and randomly assign color to annular sectors? J.M. showed an interesting way to create a sector graphic using FilledCurve. Unfortunately it ...
1
vote
0answers
145 views

How to write my own interpolation method [duplicate]

I was comparing results of spline interpolation in Mathematica and C++/gsl-library Results of interpolation are different if I use ...
0
votes
0answers
95 views

How can I make a pretzel shape using bezier curves?

I am trying to make a pretzel shape,but I cannot seem to get the loops even. Eventually, I need to make the pretzel shape loop in 3D so I need to nail the 2D concept first. Here's what I have so far. ...
7
votes
2answers
329 views

How to create an adjustable Bézier curve?

I tried to create an adjustable Bézier curve with the following simple code. However the curve didn't show up. What is the problem? Please help. ...
4
votes
3answers
269 views

How to find a length of a curve constructed using Spline?

By fitting the data using spline, I have created a curve. sp = SplineFit[data1, Cubic] I am trying to divide this curve into small segments of equal length. To ...
7
votes
0answers
83 views

Color Snapping When Using VertexColors with a Tube with BSplineCurve as an Argument

I think I've identified a bug in how VertexColors are treated when rendering a Tube object where the underlying data is a ...
6
votes
2answers
160 views

How do I get my spline based arrows to have rounded ends?

I would like to change the how the ends of the spline arrows in my figure are rendered to be "rounded", but ...
1
vote
1answer
71 views

Bspline weights

I change weigts of my points, but nothing has changed. What should i do to solve this problem? ...
1
vote
1answer
64 views

BSplineSurface problem

Why does the result of this function is straight line.If problem is in the order of my points, what order is correct? ...
4
votes
1answer
154 views

Find GeometricTransform from 3D object external surfaces to a positional point cloud data

I am looking for another way to approach this problem. Any suggestion on how to optimize the computing speed is welcome. I have a BSplineFunction which accurately ...
1
vote
1answer
136 views

What extrapolation method does Interpolation use by default? [closed]

As far as I can tell, Interpolation uses cubic spline interpolation by default - please correct me if I'm wrong. What does it use for extrapolation outside of the ...
4
votes
2answers
325 views

How to get a uniformly distributed list of points from a B-spline function [duplicate]

I created a spline function from a list of points and made a plot as follows: ...
9
votes
3answers
188 views

How to deal with the condition $u_i=u_{i+1}$ in B-Spline basis function?

The defintion of B-Spline basis function as shown below: Let $\vec{U}=\{u_0,u_1,\ldots,u_m\}$ a nondecreasing sequence of real numbers,i.e, $u_i\leq u_{i+1}\quad i=0,1,2\ldots m-1$ $$N_{i,0}(u)= ...
6
votes
2answers
264 views

2D smoothing spline interpolation

Does Mathematica have 2D smoothing spline interpolation built in? I requires an interpolation method with smooth first derivatives and cubic bivariate splines fulfill this nicely. In python I would ...
13
votes
1answer
761 views

Curve fit based on minimal data

Inspired by the fantastic answers here and here, I would like to ask a questions along similar lines. I have 6 curve types that follow these rules: Type A: If point 1 is positive and point 2 is ...
0
votes
1answer
134 views

PolarPlot works, ParametricPlot doesn't [closed]

Am new to Mathematica, so if this question has been asked already, apologies. Have a (polar) spline function and Mathematica did a fine job of calculating from my inputs and giving me the piecewise ...
12
votes
5answers
480 views
2
votes
0answers
121 views

Exporting BSplineSurface to STL

I have encountered some difficulties getting BSplineSurface to export to STL. The following code works and generates a triangulated polygon mesh from the NURBS ...
2
votes
1answer
119 views

How to generate specific function using BSpline command/

I want to generate an approximation function that fits a curve to points. My goal is to obtain an actual formula. Is this possible with the BSpline function? Using the following code: ...
0
votes
2answers
151 views

How to fix problems solving for values of BSpline function?

I generated a spline function called f using the BSplineFunction with domain {t,0,1}. ...
3
votes
1answer
126 views

How to color a BSplineSurface

I am trying to color a BSplineSurface in a complex way but not having any luck using ColorFunction. I can use ...
0
votes
4answers
159 views

Minimization in single component of BSpline to extract points

I smoothed some data with a BSpline $B[t] = (x[t],y[t])$. I would like to extract certain points from this spline by their x-Values, $x_0$. The easiest way I came up with was to minimize ...
3
votes
2answers
881 views

Generating x,y coordinates for an edge detection

I'd like to be able to process a number of graphics that have edge contours and output a list of $x$, $y$ coordinates to be used for generating a spline in another program, or in Mathematica, to make ...
10
votes
3answers
750 views

Finding “Maxima” and “Minima” on a B-Spline

I need to find the "Maxima" and "Minima" on a B-Spline or more correct the points where the 2nd components of the derivate equal zero. For example: ...
2
votes
1answer
140 views
5
votes
2answers
427 views

Intersection of two splines

I have a collection of sets of points, each set defining the segment of a (nice) curve on the unit sphere $S^2 \subset \mathbb{R}^3$. The points are computed numerically. I now want to compute the ...
7
votes
1answer
159 views

Fixing Spline curves so as to not overlap with themselves - (Diagrams)

Statement of the problem: Conceptually, what I'm trying to achieve is pretty simple. I have some code that generates a set of diagrams from a list of sets of points using BSplineCurve. Certain ...
1
vote
1answer
220 views

BSplinefunction and its derivative

Hi I am trying to use curve fit some data using the BSplinefunction. I havent been using Mathematica long, so my questions might be quite basic. ...
0
votes
1answer
381 views

Exporting B Spline Function to Excel

I am trying to export the data from a B Spline Function to a table in excel. I have tried exporting as many different file types (.xls, .txt, .dat), but all of them show up in excel as all of the ...
4
votes
3answers
892 views

Inverting a Spline-Function (Bezier or BSpline)

I would like to use a Spline-Function to describe a transformation from one range of reals to another, that is I would like to have a function which maps a value $y$ on $x$ and for simplicity let us ...
6
votes
1answer
468 views

BSplineCurve Interpolation

Can I get interpolated values from this B-spline, (shown in red)? ...
2
votes
2answers
276 views

Evaluating Polynomials at Grid Points

I am continuing my quest on B-splines. The code below builds a 5x5 matrix out of B-splines, using the BSplineBasis[] routine. I now want to evaluate the polynomials that are stored in each matrix ...