1 -- Created on: 1993-03-24
2 -- Created by: Philippe DAUTRY
3 -- Copyright (c) 1993-1999 Matra Datavision
4 -- Copyright (c) 1999-2012 OPEN CASCADE SAS
6 -- The content of this file is subject to the Open CASCADE Technology Public
7 -- License Version 6.5 (the "License"). You may not use the content of this file
8 -- except in compliance with the License. Please obtain a copy of the License
9 -- at http://www.opencascade.org and read it completely before using this file.
11 -- The Initial Developer of the Original Code is Open CASCADE S.A.S., having its
12 -- main offices at: 1, place des Freres Montgolfier, 78280 Guyancourt, France.
14 -- The Original Code and all software distributed under the License is
15 -- distributed on an "AS IS" basis, without warranty of any kind, and the
16 -- Initial Developer hereby disclaims all such warranties, including without
17 -- limitation, any warranties of merchantability, fitness for a particular
18 -- purpose or non-infringement. Please see the License for the specific terms
19 -- and conditions governing the rights and limitations under the License.
24 class OffsetCurve from Geom2d inherits Curve from Geom2d
28 -- This class implements the basis services for the creation,
29 -- edition, modification and evaluation of planar offset curve.
30 -- The offset curve is obtained by offsetting by distance along
31 -- the normal to a basis curve defined in 2D space.
32 -- The offset curve in this package can be a self intersecting
33 -- curve even if the basis curve does not self-intersect.
34 -- The self intersecting portions are not deleted at the
36 -- An offset curve is a curve at constant distance (Offset) from a
37 -- basis curve and the offset curve takes its parametrization from
38 -- the basis curve. The Offset curve is in the direction of the
39 -- normal to the basis curve N.
40 -- The distance offset may be positive or negative to indicate the
41 -- preferred side of the curve :
42 -- . distance offset >0 => the curve is in the direction of N
43 -- . distance offset >0 => the curve is in the direction of - N
44 -- On the Offset curve :
45 -- Value(u) = BasisCurve.Value(U) + (Offset * (T ^ Z)) / ||T ^ Z||
46 -- where T is the tangent vector to the basis curve and Z the
47 -- direction of the normal vector to the plane of the curve,
48 -- N = T ^ Z defines the offset direction and should not have
52 -- In this package we suppose that the continuity of the offset
53 -- curve is one degree less than the continuity of the
54 -- basis curve and we don't check that at any point ||T^Z|| != 0.0
56 -- So to evaluate the curve it is better to check that the offset
57 -- curve is well defined at any point because an exception could
58 -- be raised. The check is not done in this package at the creation
59 -- of the offset curve because the control needs the use of an
60 -- algorithm which cannot be implemented in this package.
61 -- The OffsetCurve is closed if the first point and the last point
62 -- are the same (The distance between these two points is lower or
63 -- equal to the Resolution sea package gp) . The OffsetCurve can be
64 -- closed even if the basis curve is not closed.
75 raises ConstructionError from Standard,
76 RangeError from Standard,
77 NoSuchObject from Standard,
78 UndefinedDerivative from Geom2d,
79 UndefinedValue from Geom2d,
80 NotImplemented from Standard
87 Create (C : Curve from Geom2d; Offset : Real) returns mutable OffsetCurve
88 --- Purpose : Constructs a curve offset from the basis curve C,
89 -- where Offset is the distance between the offset
90 -- curve and the basis curve at any point.
91 -- A point on the offset curve is built by measuring the
92 -- offset value along a normal vector at a point on C.
93 -- This normal vector is obtained by rotating the
94 -- vector tangential to C at 90 degrees in the
95 -- anti-trigonometric sense. The side of C on which
96 -- the offset value is measured is indicated by this
97 -- normal vector if Offset is positive, or in the inverse
98 -- sense if Offset is negative.
100 -- In this package the entities are not shared. The OffsetCurve is
101 -- built with a copy of the curve C. So when C is modified the
102 -- OffsetCurve is not modified
103 -- Warning! ConstructionError raised if the basis curve C is not at least C1.
104 -- No check is done to know if ||V^Z|| != 0.0 at any point.
105 raises ConstructionError;
109 Reverse (me : mutable);
110 --- Purpose : Changes the direction of parametrization of <me>.
112 -- - the basis curve is reversed,
113 -- - the start point of the initial curve becomes the end
114 -- point of the reversed curve,
115 -- - the end point of the initial curve becomes the start
116 -- point of the reversed curve, and
117 -- - the first and last parameters are recomputed.
120 ReversedParameter(me; U : Real) returns Real;
121 ---Purpose: Computes the parameter on the reversed curve for
122 -- the point of parameter U on this offset curve.
125 SetBasisCurve (me : mutable; C : Curve from Geom2d)
126 raises ConstructionError;
127 --- Purpose : Changes this offset curve by assigning C as the
128 -- basis curve from which it is built.
130 -- Standard_ConstructionError if the curve C is not at least "C1" continuous.
132 SetOffsetValue (me : mutable; D : Real);
133 --- Purpose : Changes this offset curve by assigning D as the offset value.
135 BasisCurve (me) returns Curve from Geom2d;
136 --- Purpose : Returns the basis curve of this offset curve. The basis curve can be an offset curve.
140 Continuity (me) returns Shape from GeomAbs;
142 -- Continuity of the Offset curve :
143 -- C0 : only geometric continuity,
144 -- C1 : continuity of the first derivative all along the Curve,
145 -- C2 : continuity of the second derivative all along the Curve,
146 -- C3 : continuity of the third derivative all along the Curve,
147 -- G1 : tangency continuity all along the Curve,
148 -- G2 : curvature continuity all along the Curve,
149 -- CN : the order of continuity is infinite.
151 -- Returns the continuity of the basis curve - 1.
152 -- The offset curve must have a unique normal direction defined
159 --- Purpose : Value and derivatives
162 -- The exception UndefinedValue or UndefinedDerivative is
163 -- raised if it is not possible to compute a unique offset
165 -- If T is the first derivative with not null length and
166 -- Z the direction normal to the plane of the curve, the
167 -- relation ||T(U) ^ Z|| != 0 must be satisfied to evaluate
169 -- No check is done at the creation time and we suppose
170 -- in this package that the offset curve is well defined.
173 D0 (me; U : Real; P : out Pnt2d)
174 raises UndefinedValue;
175 ---Purpose: Warning! this should not be called
176 -- if the basis curve is not at least C1. Nevertheless
177 -- if used on portion where the curve is C1, it is OK
181 D1 (me; U : Real; P : out Pnt2d; V1 : out Vec2d)
182 raises UndefinedDerivative;
183 ---Purpose: Warning! this should not be called
184 -- if the continuity of the basis curve is not C2.
185 -- Nevertheless, it's OK to use it on portion
186 -- where the curve is C2
190 D2 (me; U : Real; P : out Pnt2d; V1, V2 : out Vec2d)
191 raises UndefinedDerivative;
192 ---Purpose: Warning! This should not be called
193 -- if the continuity of the basis curve is not C3.
194 -- Nevertheless, it's OK to use it on portion
195 -- where the curve is C3
197 D3 (me; U : Real; P : out Pnt2d; V1, V2, V3 : out Vec2d)
198 raises UndefinedDerivative;
200 ---Purpose: Warning! This should not be called
201 -- if the continuity of the basis curve is not C4.
202 -- Nevertheless, it's OK to use it on portion
203 -- where the curve is C4
205 DN (me; U : Real; N : Integer) returns Vec2d
206 --- Purpose : The returned vector gives the value of the derivative
207 -- for the order of derivation N.
208 -- Warning! this should not be called
209 -- raises UndefunedDerivative if the continuity of the basis curve is not CN+1.
210 -- Nevertheless, it's OK to use it on portion
211 -- where the curve is CN+1
212 -- raises RangeError if N < 1.
213 -- raises NotImplemented if N > 3.
215 raises UndefinedDerivative,
222 --- Purpose : The following functions compute the value and derivatives
223 -- on the offset curve and returns the derivatives on the
225 -- The computation of the value and derivatives on the basis
226 -- curve are used to evaluate the offset curve
228 -- The exception UndefinedValue or UndefinedDerivative is
229 -- raised if it is not possible to compute a unique offset direction.
232 Value (me; U : Real; P, Pbasis : out Pnt2d; V1basis : out Vec2d)
233 raises UndefinedValue;
235 ---Purpose: Warning! this should not be called
236 -- if the basis curve is not at least C1. Nevertheless
237 -- if used on portion where the curve is C1, it is OK
240 D1 (me; U : Real; P, Pbasis : out Pnt2d;
241 V1, V1basis, V2basis : out Vec2d)
242 raises UndefinedDerivative;
244 ---Purpose: Warning! this should not be called
245 -- if the continuity of the basis curve is not C1.
246 -- Nevertheless, it's OK to use it on portion
247 -- where the curve is C1
249 D2 (me; U : Real; P, Pbasis : out Pnt2d; V1, V2, V1basis, V2basis,
251 raises UndefinedDerivative;
253 ---Purpose: Warning! this should not be called
254 -- if the continuity of the basis curve is not C3.
255 -- Nevertheless, it's OK to use it on portion
256 -- where the curve is C3
258 FirstParameter (me) returns Real;
260 LastParameter (me) returns Real;
261 ---Purpose: Returns the value of the first or last parameter of this
262 -- offset curve. The first parameter corresponds to the
263 -- start point of the curve. The last parameter
264 -- corresponds to the end point.
265 -- Note: the first and last parameters of this offset curve
266 -- are also the ones of its basis curve.
268 Offset (me) returns Real;
269 ---Purpose: Returns the offset value of this offset curve.
271 IsClosed (me) returns Boolean;
273 -- Returns True if the distance between the start point
274 -- and the end point of the curve is lower or equal to
275 -- Resolution from package gp.
278 IsCN (me; N : Integer) returns Boolean
279 --- Purpose : Is the order of continuity of the curve N ?
281 -- This method answer True if the continuity of the basis curve
282 -- is N + 1. We suppose in this class that a normal direction
283 -- to the basis curve (used to compute the offset curve) is
284 -- defined at any point on the basis curve.
286 --- Purpose : Raised if N < 0.
289 IsPeriodic (me) returns Boolean;
290 --- Purpose : Is the parametrization of a curve is periodic ?
291 -- If the basis curve is a circle or an ellipse the corresponding
292 -- OffsetCurve is periodic. If the basis curve can't be periodic
293 -- (for example BezierCurve) the OffsetCurve can't be periodic.
296 Period (me) returns Real from Standard
297 ---Purpose: Returns the period of this offset curve, i.e. the period
298 -- of the basis curve of this offset curve.
300 -- Standard_NoSuchObject if the basis curve is not periodic.
301 raises NoSuchObject from Standard
305 Transform (me : mutable; T : Trsf2d);
306 ---Purpose : Applies the transformation T to this offset curve.
307 -- Note: the basis curve is also modified.
309 TransformedParameter(me; U : Real; T : Trsf2d from gp) returns Real
310 ---Purpose: Returns the parameter on the transformed curve for
311 -- the transform of the point of parameter U on <me>.
313 -- me->Transformed(T)->Value(me->TransformedParameter(U,T))
315 -- is the same point as
317 -- me->Value(U).Transformed(T)
319 -- This methods calls the basis curve method.
322 ParametricTransformation(me; T : Trsf2d from gp) returns Real
323 ---Purpose: Returns a coefficient to compute the parameter on
324 -- the transformed curve for the transform of the
327 -- Transformed(T)->Value(U * ParametricTransformation(T))
329 -- is the same point as
331 -- Value(U).Transformed(T)
333 -- This methods calls the basis curve method.
338 Copy (me) returns mutable like me;
339 ---Purpose: Creates a new object, which is a copy of this offset curve.
342 basisCurve : Curve from Geom2d;