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1 | -- Created on: 1993-03-24 |
2 | -- Created by: Philippe DAUTRY |
3 | -- Copyright (c) 1993-1999 Matra Datavision |
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4 | -- Copyright (c) 1999-2014 OPEN CASCADE SAS |
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5 | -- |
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6 | -- This file is part of Open CASCADE Technology software library. |
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7 | -- |
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8 | -- This library is free software; you can redistribute it and/or modify it under |
9 | -- the terms of the GNU Lesser General Public License version 2.1 as published |
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10 | -- by the Free Software Foundation, with special exception defined in the file |
11 | -- OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT |
12 | -- distribution for complete text of the license and disclaimer of any warranty. |
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13 | -- |
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14 | -- Alternatively, this file may be used under the terms of Open CASCADE |
15 | -- commercial license or contractual agreement. |
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16 | |
17 | class OffsetCurve from Geom2d inherits Curve from Geom2d |
18 | |
19 | |
20 | --- Purpose : |
21 | -- This class implements the basis services for the creation, |
22 | -- edition, modification and evaluation of planar offset curve. |
23 | -- The offset curve is obtained by offsetting by distance along |
24 | -- the normal to a basis curve defined in 2D space. |
25 | -- The offset curve in this package can be a self intersecting |
26 | -- curve even if the basis curve does not self-intersect. |
27 | -- The self intersecting portions are not deleted at the |
28 | -- construction time. |
29 | -- An offset curve is a curve at constant distance (Offset) from a |
30 | -- basis curve and the offset curve takes its parametrization from |
31 | -- the basis curve. The Offset curve is in the direction of the |
32 | -- normal to the basis curve N. |
33 | -- The distance offset may be positive or negative to indicate the |
34 | -- preferred side of the curve : |
35 | -- . distance offset >0 => the curve is in the direction of N |
36 | -- . distance offset >0 => the curve is in the direction of - N |
37 | -- On the Offset curve : |
38 | -- Value(u) = BasisCurve.Value(U) + (Offset * (T ^ Z)) / ||T ^ Z|| |
39 | -- where T is the tangent vector to the basis curve and Z the |
40 | -- direction of the normal vector to the plane of the curve, |
41 | -- N = T ^ Z defines the offset direction and should not have |
42 | -- null length. |
43 | -- |
44 | -- Warnings : |
45 | -- In this package we suppose that the continuity of the offset |
46 | -- curve is one degree less than the continuity of the |
47 | -- basis curve and we don't check that at any point ||T^Z|| != 0.0 |
48 | -- |
49 | -- So to evaluate the curve it is better to check that the offset |
50 | -- curve is well defined at any point because an exception could |
51 | -- be raised. The check is not done in this package at the creation |
52 | -- of the offset curve because the control needs the use of an |
53 | -- algorithm which cannot be implemented in this package. |
54 | -- The OffsetCurve is closed if the first point and the last point |
55 | -- are the same (The distance between these two points is lower or |
56 | -- equal to the Resolution sea package gp) . The OffsetCurve can be |
57 | -- closed even if the basis curve is not closed. |
58 | |
59 | uses Dir2d from gp, |
60 | Pnt2d from gp, |
61 | Trsf2d from gp, |
62 | Vec2d from gp, |
63 | Curve from Geom2d, |
64 | Geometry from Geom2d, |
65 | Shape from GeomAbs |
66 | |
67 | |
68 | raises ConstructionError from Standard, |
69 | RangeError from Standard, |
70 | NoSuchObject from Standard, |
71 | UndefinedDerivative from Geom2d, |
72 | UndefinedValue from Geom2d, |
73 | NotImplemented from Standard |
74 | |
75 | |
76 | |
77 | is |
78 | |
79 | |
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80 | Create (C : Curve from Geom2d; |
81 | Offset : Real; |
82 | isNotCheckC0 : Boolean = Standard_False) |
83 | |
84 | returns OffsetCurve |
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85 | --- Purpose : Constructs a curve offset from the basis curve C, |
86 | -- where Offset is the distance between the offset |
87 | -- curve and the basis curve at any point. |
88 | -- A point on the offset curve is built by measuring the |
89 | -- offset value along a normal vector at a point on C. |
90 | -- This normal vector is obtained by rotating the |
91 | -- vector tangential to C at 90 degrees in the |
92 | -- anti-trigonometric sense. The side of C on which |
93 | -- the offset value is measured is indicated by this |
94 | -- normal vector if Offset is positive, or in the inverse |
95 | -- sense if Offset is negative. |
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96 | -- If isNotCheckC0 = TRUE checking if basis curve has C0-continuity |
97 | -- is not made. |
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98 | -- Warnings : |
99 | -- In this package the entities are not shared. The OffsetCurve is |
100 | -- built with a copy of the curve C. So when C is modified the |
101 | -- OffsetCurve is not modified |
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102 | -- Warning! if isNotCheckC0 = false, |
103 | -- ConstructionError raised if the basis curve C is not at least C1. |
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104 | -- No check is done to know if ||V^Z|| != 0.0 at any point. |
105 | raises ConstructionError; |
106 | |
107 | |
108 | |
109 | Reverse (me : mutable); |
110 | --- Purpose : Changes the direction of parametrization of <me>. |
111 | -- As a result: |
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. |
118 | |
119 | |
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. |
123 | |
124 | |
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125 | SetBasisCurve ( me : mutable; |
126 | C : Curve from Geom2d; |
127 | isNotCheckC0 : Boolean = Standard_False) |
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128 | raises ConstructionError; |
129 | --- Purpose : Changes this offset curve by assigning C as the |
130 | -- basis curve from which it is built. |
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131 | -- If isNotCheckC0 = TRUE checking if basis curve has C0-continuity |
132 | -- is not made. |
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133 | -- Exceptions |
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134 | -- if isNotCheckC0 = false, |
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135 | -- Standard_ConstructionError if the curve C is not at least "C1" continuous. |
136 | |
137 | SetOffsetValue (me : mutable; D : Real); |
138 | --- Purpose : Changes this offset curve by assigning D as the offset value. |
139 | |
140 | BasisCurve (me) returns Curve from Geom2d; |
141 | --- Purpose : Returns the basis curve of this offset curve. The basis curve can be an offset curve. |
142 | |
143 | |
144 | |
145 | Continuity (me) returns Shape from GeomAbs; |
146 | --- Purpose : |
147 | -- Continuity of the Offset curve : |
148 | -- C0 : only geometric continuity, |
149 | -- C1 : continuity of the first derivative all along the Curve, |
150 | -- C2 : continuity of the second derivative all along the Curve, |
151 | -- C3 : continuity of the third derivative all along the Curve, |
152 | -- G1 : tangency continuity all along the Curve, |
153 | -- G2 : curvature continuity all along the Curve, |
154 | -- CN : the order of continuity is infinite. |
155 | -- Warnings : |
156 | -- Returns the continuity of the basis curve - 1. |
157 | -- The offset curve must have a unique normal direction defined |
158 | -- at any point. |
159 | |
160 | |
161 | |
162 | |
163 | |
164 | --- Purpose : Value and derivatives |
165 | -- |
166 | -- Warnings : |
167 | -- The exception UndefinedValue or UndefinedDerivative is |
168 | -- raised if it is not possible to compute a unique offset |
169 | -- direction. |
170 | -- If T is the first derivative with not null length and |
171 | -- Z the direction normal to the plane of the curve, the |
172 | -- relation ||T(U) ^ Z|| != 0 must be satisfied to evaluate |
173 | -- the offset curve. |
174 | -- No check is done at the creation time and we suppose |
175 | -- in this package that the offset curve is well defined. |
176 | |
177 | |
178 | D0 (me; U : Real; P : out Pnt2d) |
179 | raises UndefinedValue; |
180 | ---Purpose: Warning! this should not be called |
181 | -- if the basis curve is not at least C1. Nevertheless |
182 | -- if used on portion where the curve is C1, it is OK |
183 | |
184 | |
185 | |
186 | D1 (me; U : Real; P : out Pnt2d; V1 : out Vec2d) |
187 | raises UndefinedDerivative; |
188 | ---Purpose: Warning! this should not be called |
189 | -- if the continuity of the basis curve is not C2. |
190 | -- Nevertheless, it's OK to use it on portion |
191 | -- where the curve is C2 |
192 | |
193 | |
194 | |
195 | D2 (me; U : Real; P : out Pnt2d; V1, V2 : out Vec2d) |
196 | raises UndefinedDerivative; |
197 | ---Purpose: Warning! This should not be called |
198 | -- if the continuity of the basis curve is not C3. |
199 | -- Nevertheless, it's OK to use it on portion |
200 | -- where the curve is C3 |
201 | |
202 | D3 (me; U : Real; P : out Pnt2d; V1, V2, V3 : out Vec2d) |
203 | raises UndefinedDerivative; |
204 | |
205 | ---Purpose: Warning! This should not be called |
206 | -- if the continuity of the basis curve is not C4. |
207 | -- Nevertheless, it's OK to use it on portion |
208 | -- where the curve is C4 |
209 | |
210 | DN (me; U : Real; N : Integer) returns Vec2d |
211 | --- Purpose : The returned vector gives the value of the derivative |
212 | -- for the order of derivation N. |
213 | -- Warning! this should not be called |
214 | -- raises UndefunedDerivative if the continuity of the basis curve is not CN+1. |
215 | -- Nevertheless, it's OK to use it on portion |
216 | -- where the curve is CN+1 |
217 | -- raises RangeError if N < 1. |
218 | -- raises NotImplemented if N > 3. |
219 | |
220 | raises UndefinedDerivative, |
221 | |
222 | RangeError, |
223 | NotImplemented; |
224 | |
225 | |
226 | |
227 | --- Purpose : The following functions compute the value and derivatives |
228 | -- on the offset curve and returns the derivatives on the |
229 | -- basis curve too. |
230 | -- The computation of the value and derivatives on the basis |
231 | -- curve are used to evaluate the offset curve |
232 | -- Warnings : |
233 | -- The exception UndefinedValue or UndefinedDerivative is |
234 | -- raised if it is not possible to compute a unique offset direction. |
235 | |
236 | |
237 | Value (me; U : Real; P, Pbasis : out Pnt2d; V1basis : out Vec2d) |
238 | raises UndefinedValue; |
239 | |
240 | ---Purpose: Warning! this should not be called |
241 | -- if the basis curve is not at least C1. Nevertheless |
242 | -- if used on portion where the curve is C1, it is OK |
243 | |
244 | |
245 | D1 (me; U : Real; P, Pbasis : out Pnt2d; |
246 | V1, V1basis, V2basis : out Vec2d) |
247 | raises UndefinedDerivative; |
248 | |
249 | ---Purpose: Warning! this should not be called |
250 | -- if the continuity of the basis curve is not C1. |
251 | -- Nevertheless, it's OK to use it on portion |
252 | -- where the curve is C1 |
253 | |
254 | D2 (me; U : Real; P, Pbasis : out Pnt2d; V1, V2, V1basis, V2basis, |
255 | V3basis : out Vec2d) |
256 | raises UndefinedDerivative; |
257 | |
258 | ---Purpose: Warning! this should not be called |
259 | -- if the continuity of the basis curve is not C3. |
260 | -- Nevertheless, it's OK to use it on portion |
261 | -- where the curve is C3 |
262 | |
263 | FirstParameter (me) returns Real; |
264 | |
265 | LastParameter (me) returns Real; |
266 | ---Purpose: Returns the value of the first or last parameter of this |
267 | -- offset curve. The first parameter corresponds to the |
268 | -- start point of the curve. The last parameter |
269 | -- corresponds to the end point. |
270 | -- Note: the first and last parameters of this offset curve |
271 | -- are also the ones of its basis curve. |
272 | |
273 | Offset (me) returns Real; |
274 | ---Purpose: Returns the offset value of this offset curve. |
275 | |
276 | IsClosed (me) returns Boolean; |
277 | --- Purpose : |
278 | -- Returns True if the distance between the start point |
279 | -- and the end point of the curve is lower or equal to |
280 | -- Resolution from package gp. |
281 | |
282 | |
283 | IsCN (me; N : Integer) returns Boolean |
284 | --- Purpose : Is the order of continuity of the curve N ? |
285 | -- Warnings : |
286 | -- This method answer True if the continuity of the basis curve |
287 | -- is N + 1. We suppose in this class that a normal direction |
288 | -- to the basis curve (used to compute the offset curve) is |
289 | -- defined at any point on the basis curve. |
290 | raises RangeError; |
291 | --- Purpose : Raised if N < 0. |
292 | |
293 | |
294 | IsPeriodic (me) returns Boolean; |
295 | --- Purpose : Is the parametrization of a curve is periodic ? |
296 | -- If the basis curve is a circle or an ellipse the corresponding |
297 | -- OffsetCurve is periodic. If the basis curve can't be periodic |
298 | -- (for example BezierCurve) the OffsetCurve can't be periodic. |
299 | |
300 | |
301 | Period (me) returns Real from Standard |
302 | ---Purpose: Returns the period of this offset curve, i.e. the period |
303 | -- of the basis curve of this offset curve. |
304 | -- Exceptions |
305 | -- Standard_NoSuchObject if the basis curve is not periodic. |
306 | raises NoSuchObject from Standard |
307 | is redefined; |
308 | |
309 | |
310 | Transform (me : mutable; T : Trsf2d); |
311 | ---Purpose : Applies the transformation T to this offset curve. |
312 | -- Note: the basis curve is also modified. |
313 | |
314 | TransformedParameter(me; U : Real; T : Trsf2d from gp) returns Real |
315 | ---Purpose: Returns the parameter on the transformed curve for |
316 | -- the transform of the point of parameter U on <me>. |
317 | -- |
318 | -- me->Transformed(T)->Value(me->TransformedParameter(U,T)) |
319 | -- |
320 | -- is the same point as |
321 | -- |
322 | -- me->Value(U).Transformed(T) |
323 | -- |
324 | -- This methods calls the basis curve method. |
325 | is redefined; |
326 | |
327 | ParametricTransformation(me; T : Trsf2d from gp) returns Real |
328 | ---Purpose: Returns a coefficient to compute the parameter on |
329 | -- the transformed curve for the transform of the |
330 | -- point on <me>. |
331 | -- |
332 | -- Transformed(T)->Value(U * ParametricTransformation(T)) |
333 | -- |
334 | -- is the same point as |
335 | -- |
336 | -- Value(U).Transformed(T) |
337 | -- |
338 | -- This methods calls the basis curve method. |
339 | is redefined; |
340 | |
341 | |
342 | |
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343 | Copy (me) returns like me; |
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344 | ---Purpose: Creates a new object, which is a copy of this offset curve. |
345 | |
346 | GetBasisCurveContinuity(me) |
347 | returns Shape from GeomAbs; |
348 | ---Purpose: Returns continuity of the basis curve. |
349 | |
350 | |
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351 | fields |
352 | |
353 | basisCurve : Curve from Geom2d; |
354 | offsetValue : Real; |
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355 | myBasisCurveContinuity : Shape from GeomAbs; |
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356 | |
357 | end; |