# What is a Knot Vector and How Do You Define It?

• mymachine
In summary, the conversation discusses the concept of a knot vector in mathematics and how it relates to defining points on a broken line. The website mentioned provides additional information on the topic.
mymachine
Could someone show me which one is called by the knot vector and how to define it?

Thank you

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This may help:

http://www.rhino3d.com/nurbs/

It mentions that the knot vector is a list of numbers not a real vector so maybe its related to the point numbering.

There are a number of different definitions of "knot" in different types of mathematics. From your graph it appears that you are approximating a function by a "broken line". In this case the "knots" are the points at which the different line segments join so your "knot vector" is simply (b0, b1, b2, b3).

## 1. What is a knot vector?

A knot vector is a mathematical representation of the placement and order of knots in a spline curve or surface. It is a set of numbers that determine the location of the knots and the degree of the curve.

## 2. How is a knot vector used in spline interpolation?

A knot vector is used to define the shape and behavior of a spline curve or surface. It determines the smoothness and flexibility of the interpolation, as well as the number of control points that can be used to manipulate the curve.

## 3. What are the differences between uniform and non-uniform knot vectors?

Uniform knot vectors have a constant spacing between each knot, resulting in a smoother and more evenly distributed curve. Non-uniform knot vectors have varying spacing between knots, allowing for more flexibility and control over the curve's shape.

## 4. How does the choice of knot vector affect the accuracy of the spline interpolation?

The choice of knot vector can greatly affect the accuracy of the spline interpolation. A poorly chosen knot vector can result in a curve that deviates significantly from the desired shape, while a well-chosen knot vector can result in a curve that closely matches the data points.

## 5. Can a knot vector be modified after it has been created?

Yes, a knot vector can be modified after it has been created. This can be useful in fine-tuning the shape and behavior of the spline curve or surface. However, care must be taken to ensure that the modifications do not significantly alter the intended interpolation or result in a non-valid curve.

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