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-- File: BSplineCurveKnotSplitting.cdl
-- Created: Thu Oct 3 15:54:16 1991
---Copyright: Matra Datavision 1991, 1992
class BSplineCurveKnotSplitting from Geom2dConvert
--- Purpose : An algorithm to determine points at which a BSpline
-- curve should be split in order to obtain arcs of the same continuity.
-- If you require curves with a minimum continuity for
-- your computation, it is useful to know the points
-- between which an arc has a continuity of a given
-- order. For a BSpline curve, the discontinuities are
-- localized at the knot values. Between two knot values
-- the BSpline is infinitely and continuously
-- differentiable. At a given knot, the continuity is equal
-- to: Degree - Mult, where Degree is the
-- degree of the BSpline curve and Mult is the multiplicity of the knot.
-- It is possible to compute the arcs which correspond to
-- this splitting using the global function
-- SplitBSplineCurve provided by the package Geom2dConvert.
-- A BSplineCurveKnotSplitting object provides a framework for:
-- - defining the curve to be analysed and the required degree of continuity,
-- - implementing the computation algorithm, and
-- - consulting the results.
uses Array1OfInteger from TColStd,
HArray1OfInteger from TColStd,
BSplineCurve from Geom2d
raises DimensionError from Standard,
RangeError from Standard
is
Create (BasisCurve : BSplineCurve from Geom2d; ContinuityRange : Integer)
returns BSplineCurveKnotSplitting
--- Purpose : Determines points at which the BSpline curve
-- BasisCurve should be split in order to obtain arcs
-- with a degree of continuity equal to ContinuityRange.
-- These points are knot values of BasisCurve. They
-- are identified by indices in the knots table of BasisCurve.
-- Use the available interrogation functions to access
-- computed values, followed by the global function
-- SplitBSplineCurve (provided by the package
-- Geom2dConvert) to split the curve.
-- Exceptions
-- Standard_RangeError if ContinuityRange is less than zero.
raises RangeError;
NbSplits (me) returns Integer is static;
--- Purpose :Returns the number of points at which the analysed
-- BSpline curve should be split, in order to obtain arcs
-- with the continuity required by this framework.
-- All these points correspond to knot values. Note that
-- the first and last points of the curve, which bound the
-- first and last arcs, are counted among these splitting points.
Splitting (me; SplitValues : in out Array1OfInteger)
--- Purpose : Loads the SplitValues table with the split knots
-- values computed in this framework. Each value in the
-- table is an index in the knots table of the BSpline
-- curve analysed by this algorithm.
-- The values in SplitValues are given in ascending
-- order and comprise the indices of the knots which
-- give the first and last points of the curve. Use two
-- consecutive values from the table as arguments of the
-- global function SplitBSplineCurve (provided by the
-- package Geom2dConvert) to split the curve.
-- Exceptions
-- Standard_DimensionError if the array SplitValues
-- was not created with the following bounds:
-- - 1, and
-- - the number of split points computed in this
-- framework (as given by the function NbSplits).
raises DimensionError
is static;
SplitValue (me; Index : Integer) returns Integer
--- Purpose :Returns the split knot of index Index to the split knots
-- table computed in this framework. The returned value
-- is an index in the knots table of the BSpline curve
-- analysed by this algorithm.
-- Notes:
-- - If Index is equal to 1, the corresponding knot
-- gives the first point of the curve.
-- - If Index is equal to the number of split knots
-- computed in this framework, the corresponding
-- point is the last point of the curve.
-- Exceptions
-- Standard_RangeError if Index is less than 1 or
-- greater than the number of split knots computed in this framework.
raises RangeError
is static;
fields
splitIndexes : HArray1OfInteger;
end BSplineCurveKnotSplitting;
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