de boor bspline algorithm

hi guys, I'm using de boor b-spline algorithm written by Levente Hunyadi. My question is: Why does he using a 3D Matrix? I don't know if can i share the code here, but his code is downloadable here: bspline The file is bspline_deboor.m

thanks :D

[John D'Errico]

Why not ask him? Given this is a fairly large set of functions, that is a question the author can answer far more easily than we could.

[Graziano Fuccio]

I asked him, but im not sure which he answer me :(

Answer 1

[Bruno Luong]

A very late answer, but as I deal myself with de Boor algorithm I look what exists out there.

If the question concerns the 3D array Pk in bspline_deboor.m then

• the first dimension is the dimension of control points (1, 2 or 3)
• the second and third fimensions are double indices of sub-intervals (or knot indices). In wikipedia it's (i,r) of d_{i,r} where the recursion formula occurs.

Usually optimized implementation people don't keep track of the indice r, since only the last r is used, and remove this index during the recursion, so only 2D is needed, see Wiki pedia link "Optimization" section.

This code b-spline algorithm written by Levente Hunyadi wastes a little bit of memory but it's fine and have clarity.