OpenCascade BRep Format Description (2)

OpenCascade BRep Format Description

eryar@163.com

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 

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