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

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19
votes
2answers
2k views

Joining and interpolating data points

I wonder what is the best practice for interpolating curves? Usually I'm using BSplineCurve and adjusting SplineWeights so it ...
11
votes
2answers
185 views

Arbitrary precision spline interpolation

Current implementation of Interpolation does not allow arbitrary precision spline interpolation. Yu-Sung Chang say here that "it is not hard to implement it ...
11
votes
1answer
1k views

Fitting a spline to data with FindFit?

I am trying to find a function that fits my almost linear data. A high order polynomial model has too much residual. So I was hoping to use Mathematica to fit splines to the curve. This is what I ...
10
votes
3answers
564 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: ...
9
votes
1answer
243 views

SplineDegree->1 does not work with BezierFunction?

This works (SplineDegree -> 2) ...
6
votes
1answer
363 views

BSplineCurve Interpolation

Can I get interpolated values from this B-spline, (shown in red)? ...
6
votes
1answer
125 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 ...
6
votes
0answers
57 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 ...
5
votes
2answers
273 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 ...
5
votes
3answers
236 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 ...
4
votes
3answers
560 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 ...
4
votes
2answers
290 views

How to make BSplineFunction pass each data point and naturally smooth?

(Old package, works good) ...
4
votes
0answers
290 views

Cubic polynomial interpolation with velocities listed rather than some points

I am trying to use the function BSplineFunction[] to create a natural cubic spline. Normally what is done is that you specify "SplineDegree -> 3" and include a list of points and it will carry out ...
3
votes
2answers
629 views

Parametric differentiable interpolation of a 2D data set

I have a set of data ...
3
votes
1answer
85 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 ...
3
votes
2answers
254 views

Convert BSplineFunction into two Interpolating Functions

Is there a way to decompose a BSplineFunction output into two functions x[t], y[t] ...
3
votes
0answers
327 views

How to make 3D object smooth?

This thread considers mathematical methods here to make the 3D object smooth but this question consider how to achieve the goal of smoothing a 3D object in Mathematica. I want to get smoother ...
2
votes
2answers
436 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 ...
2
votes
3answers
177 views

How can I find the points of B Spline functions for a specific range?

Based on this question: I have a list of bspline functions (nearly 1000) provided by applying BSplineFunction to a list of points. I want to get the points each of ...
2
votes
2answers
183 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 ...
2
votes
1answer
79 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: ...
2
votes
1answer
90 views

Problems with BSplineFunction vs. BSplineSurface

Why are those surfaces different? ...
2
votes
1answer
131 views

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

I created a spline function from a list of points and made a plot as follows: ...
2
votes
0answers
37 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 ...
1
vote
2answers
586 views

Derivative of a spline approximation

To approximate an experimental data function $f(t)$ with $t \in (t_{min},t_{max})$ I used a cubic spline $s(p)=(t(p),f(p))$ with the parameter $p \in (0,1)$ and $p = t/(t_{max}-t_{min})$ by using the ...
1
vote
1answer
157 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. ...
1
vote
0answers
234 views

Plotting derivatives of B-splines

I am trying to solve an electrodynamics problem numerically by using B-splines a basis function. Please don't ask me why, but if you really wanna know, here is the assignment. Using the following ...
0
votes
4answers
143 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 ...
0
votes
1answer
116 views

Plot hermite spline [closed]

I'm new to Mathematica and cannot figure out a way to plot a 2d hermite spline. My points are: $p_0=\{143.05;195.606\};$ $p_1=\{159.373;181.845\};$ $p_2=\{160.891;179.26\};$ $p_3=\{176.423;171.878\};$ ...
0
votes
2answers
109 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}. ...
0
votes
1answer
260 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 ...
0
votes
0answers
42 views

How to approximate a computationally expensive 5-dimensional manifold?

I have a 4-parameter family of functions, which I'll refer to as y[a, b, c, d][x]. In this notation, a, b, c, d are the 4 ...
0
votes
0answers
70 views

how to write my own interpolation method

I was comparing results of spline interpolation in Mathematica and C++/gsl-library Results of interpolation are different if I use: ...