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-- File: BSplineSurfaceKnotSplitting.cdl
-- Created: Fri Oct 4 08:44:03 1991
---Copyright: Matra Datavision 1991, 1992
class BSplineSurfaceKnotSplitting from GeomConvert
--- Purpose : An algorithm to determine isoparametric curves along
-- which a BSpline surface should be split in order to
-- obtain patches of the same continuity.
-- For a B-spline surface the discontinuities are localised at
-- the knot values. Between two knots values the B-spline is
-- infinitely continuously differentiable. For each parametric
-- direction at a knot of range index the continuity in this
-- direction 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 in the given direction.
-- If for your computation you need to have B-spline surface with a
-- minima of continuity it can be interesting to know between which
-- knot values, a B-spline patch, has a continuity of given order.
-- This algorithm computes the indexes of the knots where you should
-- split the surface, to obtain patches with a constant continuity
-- given at the construction time. If you just want to compute the
-- local derivatives on the surface you don't need to create the
-- BSpline patches, you can use the functions LocalD1, LocalD2,
-- LocalD3, LocalDN of the class BSplineSurface from package Geom.
uses BSplineSurface from Geom,
Array1OfInteger from TColStd,
HArray1OfInteger from TColStd
raises DimensionError from Standard,
RangeError from Standard
is
Create (BasisSurface : BSplineSurface;
UContinuityRange, VContinuityRange : Integer)
returns BSplineSurfaceKnotSplitting;
--- Purpose : Determines the u- and v-isoparametric curves
-- along which the BSpline surface BasisSurface
-- should be split in order to obtain patches with a
-- degree of continuity equal to UContinuityRange in
-- the u parametric direction, and to
-- VContinuityRange in the v parametric direction.
-- These isoparametric curves are defined by
-- parameters, which are BasisSurface knot values in
-- the u or v parametric direction. They are identified
-- by indices in the BasisSurface knots table in the
-- corresponding parametric direction.
-- Use the available interrogation functions to access
-- computed values, followed by the global function
-- SplitBSplineSurface (provided by the package
-- GeomConvert) to split the surface.
-- Exceptions
-- Standard_RangeError if UContinuityRange or
-- VContinuityRange is less than zero.
NbUSplits (me) returns Integer is static;
--- Purpose : Returns the number of u-isoparametric curves
-- along which the analysed BSpline surface should be
-- split in order to obtain patches with the continuity
-- required by this framework.
-- The parameters which define these curves are knot
-- values in the corresponding parametric direction.
-- Note that the four curves which bound the surface are
-- counted among these splitting curves.
NbVSplits (me) returns Integer is static;
--- Purpose : Returns the number of v-isoparametric curves
-- along which the analysed BSpline surface should be
-- split in order to obtain patches with the continuity
-- required by this framework.
-- The parameters which define these curves are knot
-- values in the corresponding parametric direction.
-- Note that the four curves which bound the surface are
-- counted among these splitting curves.
Splitting (me; USplit, VSplit : in out Array1OfInteger)
--- Purpose: Loads the USplit and VSplit tables with the split
-- knots values computed in this framework. Each value
-- in these tables is an index in the knots table
-- corresponding to the u or v parametric direction of
-- the BSpline surface analysed by this algorithm.
-- The USplit and VSplit values are given in ascending
-- order and comprise the indices of the knots which
-- give the first and last isoparametric curves of the
-- surface in the corresponding parametric direction.
-- Use two consecutive values from the USplit table and
-- two consecutive values from the VSplit table as
-- arguments of the global function
-- SplitBSplineSurface (provided by the package
-- GeomConvert) to split the surface.
-- Exceptions
-- Standard_DimensionError if:
-- - the array USplit was not created with the following bounds:
-- - 1 , and
-- - the number of split knots in the u parametric
-- direction computed in this framework (as given
-- by the function NbUSplits); or
-- - the array VSplit was not created with the following bounds:
-- - 1 , and
-- - the number of split knots in the v parametric
-- direction computed in this framework (as given
-- by the function NbVSplits).
raises DimensionError
is static;
USplitValue (me; UIndex : Integer) returns Integer
--- Purpose : Returns the split knot of index UIndex
-- to the split knots table for the u parametric direction
-- computed in this framework. The returned value is
-- an index in the knots table relative to the u
-- parametric direction of the BSpline surface analysed by this algorithm.
-- Note: If UIndex is equal to 1, or to the number of split knots for the u
-- parametric direction computed in
-- this framework, the corresponding knot gives the
-- parameter of one of the bounding curves of the surface.
-- Exceptions
-- Standard_RangeError if UIndex is less than 1 or greater than the number
-- of split knots for the u parametric direction computed in this framework.
raises RangeError
is static;
VSplitValue (me; VIndex : Integer) returns Integer
--- Purpose : Returns the split knot of index VIndex
-- to the split knots table for the v parametric direction
-- computed in this framework. The returned value is
-- an index in the knots table relative to the v
-- parametric direction of the BSpline surface analysed by this algorithm.
-- Note: If UIndex is equal to 1, or to the number of split knots for the v
-- parametric direction computed in
-- this framework, the corresponding knot gives the
-- parameter of one of the bounding curves of the surface.
-- Exceptions
-- Standard_RangeError if VIndex is less than 1 or greater than the number
-- of split knots for the v parametric direction computed in this framework.
raises RangeError
is static;
fields
usplitIndexes : HArray1OfInteger;
vsplitIndexes : HArray1OfInteger;
end BSplineSurfaceKnotSplitting;
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