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rhino:nurbs [2015/09/14] 127.0.0.1 external edit |
rhino:nurbs [2019/02/26] (current) chuck [What is NURBS geometry?] |
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The **knots** are a list of degree+N-1 numbers, where N is the number of control points. Sometimes this list of numbers is called the knot vector. In this term, the word vector does not mean 3D direction. | The **knots** are a list of degree+N-1 numbers, where N is the number of control points. Sometimes this list of numbers is called the knot vector. In this term, the word vector does not mean 3D direction. | ||

- | This list of knot numbers must satisfy several technical conditions. The standard way to satisfy the technical conditions is to require the numbers to stay the same or get larger as you go down the list and to limit the number of duplicate values to no more than the degree. For example, for a degree 3 NURBS curve with 15 control points: | + | This list of knot numbers must satisfy several technical conditions. The standard way to satisfy the technical conditions is to require the numbers to stay the same or get larger as you go down the list and to limit the number of duplicate values to no more than the degree. For example, for a degree 3 NURBS curve with 11 control points: |

* The list of numbers 0,0,0,1,2,2,2,3,7,7,9,9,9 is a satisfactory list of knots. | * The list of numbers 0,0,0,1,2,2,2,3,7,7,9,9,9 is a satisfactory list of knots. | ||

* The list 0,0,0,1,2,2,2,2,7,7,9,9,9 is unacceptable because there are four 2s and four is larger than the degree. | * The list 0,0,0,1,2,2,2,2,7,7,9,9,9 is unacceptable because there are four 2s and four is larger than the degree. |

rhino/nurbs.txt ยท Last modified: 2019/02/26 by chuck