OpenCascade BRep Format Description
摘要Abstract：本文结合OpenCascade的BRep格式描述文档和源程序，对BRep格式进行分析，详细说明BRep的数据组织形式。结合源程序，可以对OpenCascade中Modeling Data模块中的模型数据结构进行理解。
关键字Key Words：OpenCascade, BRep Format, ModelingData
一、实例分析
OpenCascade的data目录中的face1.brep文件：
1
DBRep_DrawableShape
2
3 CASCADE Topology V1, (c) Matra - Datavision
4 Locations 5
5 1
6 1 0 0 - 0.4
7 0 1 0 0
8 0 0 1 0
9 1
10 1 0 0 - 0.4
11 0 1 0 0
12 0 0 1 0
13 1
14 1 0 0 0.8
15 0 1 0 0
16 0 0 1 0
17 1
18 1 0 0 0.8
19 0 1 0 0
20 0 0 1 0
21 2 1 1 2 1 3 1 4 1 0
22 Curve2ds 8
23 1 0 0.8 1 0
24 2 0 0 1 0 0 1 0.8
25 1 1.82347658193698 0 0 1
26 1 1 - 1.77459666924148 1 0
27 1 4.45970872524261 0 0 1
28 1 1 - 0.225403330758516 1 0
29 1 0 0 1 0
30 2 0 0 1 0 0 1 0.8
31 Curves 4
32 2 0 0 0.8 0 0 1 1 0 0 0 1 0 0.8
33 1 - 0.2 0.774596669241484 0 0 0 1
34 1 - 0.2 - 0.774596669241484 0 0 0 1
35 2 0 0 0 0 0 1 1 0 0 0 1 0 0.8
36 Polygon3D 0
37 PolygonOnTriangulations 0
38 Surfaces 4
39 2 0 0 0 0 0 1 1 0 0 0 1 0 0.8
40 1 0 0 0.8 0 0 1 1 0 0 0 1 0
41 1 - 1 - 1 - 1 1 0 0 0 0 1 0 - 1 0
42 1 0 0 0 0 0 1 1 0 0 0 1 0
43 Triangulations 0
44
45 TShapes 10
46 Ve
47 2.0000002e-007
48 - 0.2 0.774596669241483 0.8
49 0 0
50
51 0101101
52 *
53 Ve
54 2.0000002e-007
55 - 0.2 - 0.774596669241484 0.8
56 0 0
57
58 0101101
59 *
60 Ed
61 1e - 007 1 1 0
62 1 1 0 1.82347658193698 4.45970872524261
63 2 1 1 0 1.82347658193698 4.45970872524261
64 2 2 2 0 1.82347658193698 4.45970872524261
65 0
66
67 0101000
68 + 10 0 - 9 0 *
69 Ve
70 2.0000002e-007
71 - 0.2 0.774596669241483 0
72 0 0
73
74 0101101
75 *
76 Ed
77 1e - 008 1 1 0
78 1 2 0 0 0.8
79 2 3 1 0 0 0.8
80 2 4 3 5 0 0.8
81 0
82
83 0101000
84 + 7 0 - 10 0 *
85 Ve
86 2.0000002e-007
87 - 0.2 - 0.774596669241484 0
88 0 0
89
90 0101101
91 *
92 Ed
93 1e - 008 1 1 0
94 1 3 0 0 0.8
95 2 5 1 0 0 0.8
96 2 6 3 5 0 0.8
97 0
98
99 0101000
100 + 5 0 - 9 0 *
101 Ed
102 1e - 007 1 1 0
103 1 4 0 1.82347658193698 4.45970872524261
104 2 7 1 0 1.82347658193698 4.45970872524261
105 2 8 4 0 1.82347658193698 4.45970872524261
106 0
107
108 0101000
109 + 7 0 - 5 0 *
110 Wi
111
112 0101100
113 - 8 0 - 6 0 + 4 0 + 3 0 *
114 Fa
115 0 1e - 007 1 0
116
117 0101000
118 + 2 0 *
119
120 + 1 0
121 0
122
123
2
3 CASCADE Topology V1, (c) Matra - Datavision
4 Locations 5
5 1
6 1 0 0 - 0.4
7 0 1 0 0
8 0 0 1 0
9 1
10 1 0 0 - 0.4
11 0 1 0 0
12 0 0 1 0
13 1
14 1 0 0 0.8
15 0 1 0 0
16 0 0 1 0
17 1
18 1 0 0 0.8
19 0 1 0 0
20 0 0 1 0
21 2 1 1 2 1 3 1 4 1 0
22 Curve2ds 8
23 1 0 0.8 1 0
24 2 0 0 1 0 0 1 0.8
25 1 1.82347658193698 0 0 1
26 1 1 - 1.77459666924148 1 0
27 1 4.45970872524261 0 0 1
28 1 1 - 0.225403330758516 1 0
29 1 0 0 1 0
30 2 0 0 1 0 0 1 0.8
31 Curves 4
32 2 0 0 0.8 0 0 1 1 0 0 0 1 0 0.8
33 1 - 0.2 0.774596669241484 0 0 0 1
34 1 - 0.2 - 0.774596669241484 0 0 0 1
35 2 0 0 0 0 0 1 1 0 0 0 1 0 0.8
36 Polygon3D 0
37 PolygonOnTriangulations 0
38 Surfaces 4
39 2 0 0 0 0 0 1 1 0 0 0 1 0 0.8
40 1 0 0 0.8 0 0 1 1 0 0 0 1 0
41 1 - 1 - 1 - 1 1 0 0 0 0 1 0 - 1 0
42 1 0 0 0 0 0 1 1 0 0 0 1 0
43 Triangulations 0
44
45 TShapes 10
46 Ve
47 2.0000002e-007
48 - 0.2 0.774596669241483 0.8
49 0 0
50
51 0101101
52 *
53 Ve
54 2.0000002e-007
55 - 0.2 - 0.774596669241484 0.8
56 0 0
57
58 0101101
59 *
60 Ed
61 1e - 007 1 1 0
62 1 1 0 1.82347658193698 4.45970872524261
63 2 1 1 0 1.82347658193698 4.45970872524261
64 2 2 2 0 1.82347658193698 4.45970872524261
65 0
66
67 0101000
68 + 10 0 - 9 0 *
69 Ve
70 2.0000002e-007
71 - 0.2 0.774596669241483 0
72 0 0
73
74 0101101
75 *
76 Ed
77 1e - 008 1 1 0
78 1 2 0 0 0.8
79 2 3 1 0 0 0.8
80 2 4 3 5 0 0.8
81 0
82
83 0101000
84 + 7 0 - 10 0 *
85 Ve
86 2.0000002e-007
87 - 0.2 - 0.774596669241484 0
88 0 0
89
90 0101101
91 *
92 Ed
93 1e - 008 1 1 0
94 1 3 0 0 0.8
95 2 5 1 0 0 0.8
96 2 6 3 5 0 0.8
97 0
98
99 0101000
100 + 5 0 - 9 0 *
101 Ed
102 1e - 007 1 1 0
103 1 4 0 1.82347658193698 4.45970872524261
104 2 7 1 0 1.82347658193698 4.45970872524261
105 2 8 4 0 1.82347658193698 4.45970872524261
106 0
107
108 0101000
109 + 7 0 - 5 0 *
110 Wi
111
112 0101100
113 - 8 0 - 6 0 + 4 0 + 3 0 *
114 Fa
115 0 1e - 007 1 0
116
117 0101000
118 + 2 0 *
119
120 + 1 0
121 0
122
123
显示结果如下图所示：
Figure 1. Wireframe mode
Figure 2. Shaded mode
二、结论
因为OpenCascade的Brep格式是自己的格式，只用到了ModelingData模块，不使用DataExchange模块，可以作为数据交换的一种格式。
三、参考资料
1. BNF范式：http://hi.baidu.com/xuyingming2012/item/9060029141427bd81b49df9e
2. BRep Format Description
3. OpenCascade source code
PDF Version: BRep Format Description
PDF Version: BRep Format Description White Paper
