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1 | -- Created on: 1994-08-03 |
2 | -- Created by: Christophe MARION |
3 | -- Copyright (c) 1994-1999 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 Algo from HLRBRep inherits InternalAlgo from HLRBRep |
18 | |
19 | ---Purpose: A framework to compute a shape as seen in a projection plane. This is done by |
20 | -- calculating the visible and the hidden parts of the shape. |
21 | -- HLRBRep_Algo works with three types of entity: |
22 | -- - shapes to be visualized |
23 | -- - edges in these shapes (these edges are |
24 | -- the basic entities which will be visualized or hidden), and |
25 | -- - faces in these shapes which hide the edges. |
26 | -- HLRBRep_Algo is based on the principle of comparing each edge of the shape to be |
27 | -- visualized with each of its faces, and calculating the visible and the hidden parts of each edge. |
28 | -- For a given projection, HLRBRep_Algo calculates a set of lines characteristic of the |
29 | -- object being represented. It is also used in conjunction with the |
30 | -- HLRBRep_HLRToShape extraction utilities, which reconstruct a new, simplified shape |
31 | -- from a selection of calculation results. This new shape is made up of edges, which |
32 | -- represent the shape visualized in the projection. |
33 | -- HLRBRep_Algo takes the shape itself into account whereas HLRBRep_PolyAlgo |
34 | -- works with a polyhedral simplification of the shape. When you use HLRBRep_Algo, you |
35 | -- obtain an exact result, whereas, when you use HLRBRep_PolyAlgo, you reduce |
36 | -- computation time but obtain polygonal segments. In the case of complicated |
37 | -- shapes, HLRBRep_Algo may be time-consuming. |
38 | -- An HLRBRep_Algo object provides a framework for: |
39 | -- - defining the point of view |
40 | -- - identifying the shape or shapes to be visualized |
41 | -- - calculating the outlines |
42 | -- - calculating the visible and hidden lines of the shape. |
43 | -- Warning |
44 | -- - Superimposed lines are not eliminated by this algorithm. |
45 | -- - There must be no unfinished objects inside the shape you wish to visualize. |
46 | -- - Points are not treated. |
47 | -- - Note that this is not the sort of algorithm used in generating shading, which |
48 | -- calculates the visible and hidden parts of each face in a shape to be visualized by |
49 | -- comparing each face in the shape with every other face in the same shape. |
50 | |
51 | uses |
52 | TShared from MMgt, |
53 | Shape from TopoDS |
54 | |
55 | is |
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56 | Create returns Algo from HLRBRep; |
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57 | ---Purpose: Constructs an empty framework for the |
58 | -- calculation of visible and hidden lines of a shape in a projection. |
59 | -- Use the function: |
60 | -- - Projector to define the point of view |
61 | -- - Add to select the shape or shapes to be visualized |
62 | -- - Update to compute the outlines of the shape, and |
63 | -- - Hide to compute the visible and hidden lines of the shape. |
64 | |
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65 | Create(A : Algo from HLRBRep) returns Algo from HLRBRep; |
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66 | |
67 | Add(me : mutable; S : Shape from TopoDS; |
68 | SData : TShared from MMgt; |
69 | nbIso : Integer from Standard = 0) |
70 | ---Purpose: add the Shape <S>. |
71 | is static; |
72 | |
73 | Add(me : mutable; S : Shape from TopoDS; |
74 | nbIso : Integer from Standard = 0) |
75 | ---Purpose: Adds the shape S to this framework, and |
76 | -- specifies the number of isoparameters nbiso desired in visualizing S. |
77 | -- You may add as many shapes as you wish. Use the function Add once for each shape. |
78 | is static; |
79 | |
80 | Index(me : mutable; S : Shape from TopoDS) |
81 | returns Integer from Standard |
82 | ---Purpose: return the index of the Shape <S> and |
83 | -- return 0 if the Shape <S> is not found. |
84 | is static; |
85 | |
86 | OutLinedShapeNullify(me : mutable) |
87 | ---Purpose: nullify all the results of OutLiner from HLRTopoBRep. |
88 | is static; |
89 | |
90 | end Algo; |