NURBS Library

[Mark Spink]

I wish to announce the NURBS library a new contribution to
SCILAB. NURBS is an acronym for Non-Uniform Rational
B-Splines. NURBS can be consider to be a special case of
more commonly known B-Splines. NURBS are used in almost all
CAD packages for the parametric design and representation of
freeform curves and surfaces. The intention of this library
is to provide an interactive enviroment through SCILAB that
algorithms using NURBS can be design, manipulated and
demonstrated. The library includes the following functions
in Version 1.0:

nrbmak - Construct a NURB from control points and knots.
nrbtform - Apply scaling, translation or rotation
operators.
nrbkntins - Knot insertion/refinement.
nrbdegelev - Degree elevation.
nrbderiv - Construction of the 1st and 2nd derivatives.
nrbdeval - Evaluation of the NURBS derivatives.
nrbkntmult - Find the multipilicity of a knot vector.
nrbreverse - Reverse evaluation direction of NURBS.
nrbtranspose - Swap U and V for NURBS surface.
nrbline - Construct a straight line.
nrbcirc - Construct a circular arc.
nrbrect - Construct a rectangle.
nrb4surf - Surface defined by 4 corner points.
nrbcylind - Cylinder or cylindrical patch.
nrbeval - Evaluation of NURBS curve or surface.
nrbextrude - Extrude a NURBS curve along a vector.
nrbrevolve - Construct surface by revolving a profile.
nrbruled - Ruled surface between two NURBS curves.
nrbcoons - Construct Coons bilinearly blended surface
patch.
nrbplot - Plot NURBS curve or surface.
bspeval - Evaluate a univariate B-Spline.
bspdeval - Evaluate the nth derivative of a univariate
B-Spline.
bspkntins - Insert a knot or knots into a univariate
B-Spline.
bspdegelev - Degree elevation of a univariate B-Spline.
vecnorm - Normalise the vectors.
vecmag - Magnitude of the vectors.
vecmag2 - Squared magnitude of the vectors.
vecangle - Alternative to atan2 (0 <= angle < 2*pi).
vecdot - Dot product of two vectors.
veccross - Cross product of two vectors.
vecrotx - Rotation around the x-axis.
vecroty - Rotation around the y-axis.
vecrotz - Rotation around the z-axis.
vecscale - Scaling.
vectrans - Translation.
deg2rad - Convert degrees to radians.

The library also contains demonstartion scripts for almost
all the functions listed above.

Currently the only documentation is the scilab help files,
and the short
description of each function at the beginning of each
library function
and the demonstration examples. I will produce a manual
sometime in the
future when I have the time.

For a detailed explaination of NURBS and how to manipulate
them, I can
strongly recommend the book by Les Piegl and Wayne Tiller
called 'The NURBS
Book' ISBN 3-540-61545-8. Please note that the 'C' code
algorithms is this
library are modified versions of the pseudo-code within the
book.

This library is open source software under the GPL version 2
license, and I'd be very happy if anyone wishes to join me
in either extending this toolbox or towards my main goal of
2D/3D meshing generation library, for which this library
will used to define the geometric attributes.

Ideas for future functions are:

nrbswung - Profile curve swung over a arbitrary
trajectory.
nrbskinned - Blending profile curves along a
trajectory.
nrbswept - Sweeping profile curve over a trajectory
curve.
nrbinterp - Interpolation of data points.
nrb2bezier - NURB decomposition into Bezier segments.
nrbsplit - Split the curve or surface into pieces.
nrbjoin - Join together curve or surface.
nrbkntdel - Knot removal.
nrbdegred - Degree reduction.

I'm also not to happy about the current implementation of
derivatives and will probably make some changes there too.

Happy NURB'ing

Mark Spink
University of Leeds, UK.
een...@ee.leeds.ac.uk

[Mark Spink]

I forgot to mention that the library is available at the
SCILAB ftp site in the contributions section:

ftp://ftp.inria.fr:/INRIA/Scilab/contrib/

There is currently no link to the library via SCILAB
homepage contributions section, however one might be added
by the maintainers soon!

http://www-rocq.inria.fr/scilab/contributions.html

Mark Spink

[Mark Spink]

The web link to the NURBS library (and many other
contributions) is now available on the scilab homesite:

http://www-rocq.inria.fr/scilab/contributions

How about that for service! :-) Thanks.

[vishwa...@gmail.com]

Hello Sir,
I want NURBS toolbox for Scilab but i am getting following error,
Not Found
The requested URL /scilab/contributions was not found on this server.

Thanks & Regards
-Vishwas

[philipp....@gmail.com]

Great Work! But unfortunately is the download Link still unavailable. Could you please provide a new one, or anybody who has already a copy?