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-- File: Law_BSplineKnotSplitting.cdl
-- Created: Fri Jan 17 14:51:42 1997
-- Author: Philippe MANGIN
-- <pmn@sgi29>
---Copyright: Matra Datavision 1997
class BSplineKnotSplitting from Law
--- Purpose :
-- For a B-spline curve the discontinuities are localised at the
-- knot values and between two knots values the B-spline is
-- infinitely continuously differentiable.
-- At a knot of range index the continuity is equal to :
-- Degree - Mult (Index) where Degree is the degree of the
-- basis B-spline functions and Mult the multiplicity of the knot
-- of range Index.
-- If for your computation you need to have B-spline curves with a
-- minima of continuity it can be interesting to know between which
-- knot values, a B-spline curve arc, has a continuity of given order.
-- This algorithm computes the indexes of the knots where you should
-- split the curve, to obtain arcs with a constant continuity given
-- at the construction time. The splitting values are in the range
-- [FirstUKnotValue, LastUKnotValue] (See class B-spline curve from
-- package Geom).
-- If you just want to compute the local derivatives on the curve you
-- don't need to create the B-spline curve arcs, you can use the
-- functions LocalD1, LocalD2, LocalD3, LocalDN of the class
-- BSplineCurve.
--- KeyWords : BSpline, Knot Splitting, Continuity
--- See Also : File BSpline from package Law
--- References :
-- Gerald Farin Curves and Surfaces for Computer Aided Geometric
-- Design.
uses Array1OfInteger from TColStd,
HArray1OfInteger from TColStd,
BSpline from Law
raises DimensionError from Standard,
RangeError from Standard
is
Create (BasisLaw : BSpline from Law; ContinuityRange : Integer)
returns BSplineKnotSplitting
--- Purpose :
-- Locates the knot values which correspond to the segmentation of
-- the curve into arcs with a continuity equal to ContinuityRange.
raises RangeError;
--- Purpose :
-- Raised if ContinuityRange is not greater or equal zero.
NbSplits (me) returns Integer is static;
--- Purpose :
-- Returns the number of knots corresponding to the splitting.
Splitting (me; SplitValues : in out Array1OfInteger)
--- Purpose :
-- Returns the indexes of the BSpline curve knots corresponding to
-- the splitting.
raises DimensionError
--- Purpose :
-- Raised if the length of SplitValues is not equal to NbSPlit.
is static;
SplitValue (me; Index : Integer) returns Integer
--- Purpose :
-- Returns the index of the knot corresponding to the splitting
-- of range Index.
raises RangeError
--- Purpose :
-- Raised if Index < 1 or Index > NbSplits
is static;
fields
splitIndexes : HArray1OfInteger;
end BSplineKnotSplitting;
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