Spline what is a b spline what is rational b spline

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Discussion Overview

The discussion centers on the definitions and characteristics of splines, specifically focusing on B-splines, rational B-splines, uniform rational B-splines, and non-uniform rational B-splines (NURBS). The scope includes theoretical aspects and technical explanations related to these mathematical constructs.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants describe a spline as a piecewise continuous and differentiable function used to approximate more complex functions, with differentiability depending on the type of spline.
  • One participant explains different types of splines, such as linear, quadratic, and cubic splines, highlighting their continuity and differentiability properties at the knots.
  • A cubic spline is noted as the most commonly used type, with historical context provided regarding the origin of the term "spline."
  • Another participant mentions that the term B-spline stands for "basis spline," indicating that splines can be expressed in terms of a basis within a vector space.
  • A simpler definition is proposed, suggesting that splines represent different methods for creating or storing curves or surfaces.

Areas of Agreement / Disagreement

The discussion presents multiple viewpoints on the definitions and characteristics of splines, with no consensus reached on a singular definition or understanding of the various types of splines mentioned.

Contextual Notes

Some definitions and properties of splines may depend on specific mathematical contexts or assumptions that are not fully detailed in the discussion.

chandran
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what is a spline

what is a b spline

what is rational b spline

what is a uniform rational b spline

what is non uniform rational b spline(NURBS)
 
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A spline is a piecewise continuous, piecewise differentiable, etc. used to approximate more complicated functions. How differentiable depends upon what kind of spline you are using.
For example, a "linear spline" is just a piecewise linear function that is continuous at the "knots"- where the linear pieces connect. Obviously, you can't require it to be differentiable there without making it just a single straight line.

A "quadratic spline" consists of quadratic functions between knots that are both continuous and differentiable where they connect- but not twice differentiable.

A "cubic spline" consists of piecewise cubics that are twice differentiable where they connect.

Cubic splines are most commonly used. In fact, the name "spline" comes from the use of "splines"- very thin flexible strips of wood used to draw complex curves (before computer design). One can show by stress arguments that they are cubic splines.

The term b-spline comes from "basis" spline. If you think of the set of all possible splines (of a particular type:quadratic, cubic, etc.), you can show that that forms a vector-space and so any such spline can be written in terms of some basis.
 
simple def'n: different ways to create or store a curve or surface.
 

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