OpenCasCade – 贴纹理

Bertha 。 2022-03-15 01:42 480阅读 0赞

## **前言** ##

因为项目需要，所以最近研究了下给 用OpenCasCade库创建的模型贴纹理的问题。因为网上没找到相关的文章，特此记录下来。

## **官方示例** ##

本文中的代码是完全仿照官方示例（All-vc10 中的 Viewer3d）所写的，筒子们可以自己去研究一下这块代码，如图：

[![2015-03-07\_153525][2015-03-07_153525]][2015-03-07_153525]

然后看下官方示例的贴纹理效果：

[![sampleBottle][]][sampleBottle]

[![sampleKitchen][]][sampleKitchen]

## **代码解读** ##

这里为简单起见，只解读图一中 **Bottle** 的代码， 代码的作用，请**仔细阅读注释**：

### **sampleBottle函数（创建Bottle，调用Texturize函数）：** ###

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 <td> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 </td> 
 <td> //通过载入brep文件，创建bottle，并贴纹理 void TexturesExt_Presentation::sampleBottle() {&nbsp;&nbsp; //创建一个bottle TopoDS_Shape aShape; if (!loadShape(aShape, "bottle.brep")) return; &nbsp; // resize and move the shape to the center of the viewer&nbsp;&nbsp;这块代码对纹理显示无贡献 gp_Trsf aTrsf1, aTrsf2; aTrsf1.SetScale(gp_Pnt(0,0,0), /*0.8*/0.1);&nbsp;&nbsp;&nbsp;&nbsp;//对 bottle 进行缩放 aTrsf2.SetTranslation(gp_Pnt(0,0,0),gp_Pnt(0,0,-20)); aTrsf1.Multiply(aTrsf2); BRepBuilderAPI_Transform Transformer(aTrsf1); Transformer.Perform(aShape); aShape = Transformer.Shape(); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; TopTools_IndexedMapOfShape aFaces; // 函数原型：static void TopExp::MapShapes(const TopoDS_Shape&amp; S, const TopAbs_ShapeEnum T, TopTools_IndexedMapOfShape&amp; M) // 第二个参数： TopAbs_ShapeEnum 是一个枚举类型，读者需要自己去读一下 // Tool to explore a topological data structure. Stores in the map &lt;M&gt; all the sub-shapes of &lt;S&gt; of type &lt;T&gt;. TopExp::MapShapes(aShape, TopAbs_FACE, aFaces); &nbsp; &nbsp; //没有这几句代码 则只显示指定贴了纹理的那些FACE，不显示瓶子整体。但同样，这段对纹理的显示没有任何贡献。 //display original shape in shaded display mode Handle_AIS_Shape aShapeIO = drawShape(aShape, Graphic3d_NOM_BRASS, Standard_False); getAISContext()-&gt;SetDisplayMode(aShapeIO, AIS_Shaded, Standard_False); // Set increased polygon offset for the main shape to avoid depth collision with textured faces aShapeIO-&gt;SetPolygonOffsets(Aspect_POM_Fill, 1.5, 0.5); DISP(aShapeIO);&nbsp;&nbsp;&nbsp;&nbsp;// #define DISP(OBJ) getAISContext()-&gt;Display((OBJ), Standard_False) &nbsp; &nbsp; //指定需要贴纹理的FACE，设置相关参数 Handle_AIS_TexturedShape aTFace1 = Texturize(aFaces(16), "carrelage1.gif", 1, 1, 3, 2); DISP(aTFace1); &nbsp; Handle_AIS_TexturedShape aTFace2 = Texturize(aFaces(21), "carrelage1.gif", 1, 1, 3, 2); DISP(aTFace2); &nbsp; //更新视图 getViewer()-&gt;Update(); } </td> 
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</table>

### **Texturize函数（贴纹理）：** ###

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 <td> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 </td> 
 <td> Handle_AIS_TexturedShape TexturesExt_Presentation::Texturize(const TopoDS_Shape&amp; aShape, TCollection_AsciiString aTFileName, Standard_Real toScaleU, Standard_Real toScaleV, Standard_Real toRepeatU, Standard_Real toRepeatV, Standard_Real originU, Standard_Real originV) { //create a textured presentation object for aShape //AIS_TexturedShape 是一个非常重要的类！下面是官方文档中的说明 //This class allows to map textures on shapes. Presentations modes AIS_WireFrame (0) and AIS_Shaded (1) behave in the same manner as in AIS_Shape &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//whilst new modes 2 (bounding box) and 3 (texture mapping) extends it functionality. //The texture itself is parametrized in (0,1)x(0,1). Each face of a shape located in UV space is provided with these parameters: //•Umin - starting position in U //•Umax - ending position in U //•Vmin - starting position in V //•Vmax - ending position in V //Each face is triangulated and a texel is assigned to each node. Facets are then filled using a linear interpolation of texture between each 'three texels'. //User can act on: //•the number of occurrences of the texture on the face //•the position of the origin of the texture //•the scale factor of the texture Handle_AIS_TexturedShape aTShape = new AIS_TexturedShape(aShape); &nbsp; TCollection_AsciiString TFileName; &nbsp; &nbsp; //load texture from file if it is not an integer value //integer value indicates a number of texture in predefined TexturesExt enumeration CString initfile(((OCC_App*) AfxGetApp())-&gt;GetInitDataDir()); initfile += "\\Data\\"; if (!aTFileName.IsIntegerValue()) { initfile += aTFileName.ToCString(); } &nbsp; aTShape-&gt;SetTextureFileName((Standard_CString)(LPCTSTR)initfile); &nbsp; // do other initialization of AIS_TexturedShape aTShape-&gt;SetTextureMapOn(); aTShape-&gt;SetTextureScale(Standard_True, toScaleU, toScaleV); aTShape-&gt;SetTextureRepeat(Standard_True, toRepeatU, toRepeatV); aTShape-&gt;SetTextureOrigin(Standard_True, originU, originV); &nbsp; aTShape-&gt;SetDisplayMode(3); // mode 3 is "textured" mode，参见上面AIS_TexturedShape类的解释 &nbsp; return aTShape; } </td> 
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至此，就可以实现上图中显示的Bottle效果。同学们可以自己创建一个简单的 box 来尝试一下，这里我给个简单的示例：

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 <td> void CneedAVView::MakeBottle() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TopoDS_Shape aRes = BRepPrimAPI_MakeBox(gp_Pnt(0,0,0),555,555,555).Shape(); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TopTools_IndexedMapOfShape aFaces; TopExp::MapShapes(aRes, TopAbs_FACE, aFaces); Handle(AIS_TexturedShape) aTFace1 = Texturize(aFaces(1), "./carrelage1.gif", 1, 1, 3, 2); DISP(aTFace1); &nbsp; Handle(AIS_TexturedShape) aTFace2 = Texturize(aFaces(2), "./carrelage1.gif", 1, 1, 3, 2);&nbsp;&nbsp;//16 21 3 2 DISP(aTFace2); &nbsp; Handle(AIS_TexturedShape) aTFace5 = Texturize(aFaces(5), "./carrelage1.gif", 1, 1, 3, 2); DISP(aTFace5); &nbsp; myView-&gt;Update(); } </td> 
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***也许你发现这样还是看不到显示的纹理！***

后来发现，需要设置这样关键的一句

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 <td> 1 </td> 
 <td> myView-&gt;SetSurfaceDetail(V3d_TEX_ALL); </td> 
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</table>

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 <td> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 </td> 
 <td> 函数原型：void V3d_View::SetSurfaceDetail(const V3d_TypeOfSurfaceDetail&nbsp;SurfaceDetail) 功&nbsp;&nbsp;&nbsp;&nbsp;能：select the kind of rendering for texture mapping no texture mapping by default &nbsp; &nbsp; 其中 V3d_TypeOfSurfaceDetail 是一个枚举类 enum V3d_TypeOfSurfaceDetail Modes of visualization for objects in a view. ·V3d_TEX_NONE: no texture mapping, ·V3d_TEX_ENVIRONMENT: environment mapping only, ·V3d_TEX_ALL: environment and texture mapping. &nbsp; Enumerator： ·V3d_TEX_NONE ·V3d_TEX_ENVIRONMENT ·V3d_TEX_ALL </td> 
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如官方文档中所述：

<table> 
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 <td> 1 </td> 
 <td> no texture mapping by default </td> 
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所以我们要显示的把参数设置为：**V3d\_TEX\_ALL**

如此，你就可以看到自己贴的纹理了，效果图如下（因为我省略了一些函数所以这里只显示了贴纹理的面（见 **sampleBottle** 函数中所述））：

[![sample][]][sample]

至此，OpenCasCade的中的贴纹理就搞定了，想了解更多，请自行阅读官方示例。

感谢原作者的知识分享。

转自按地址：[http://www.zyh1690.org/opencascade-texture/][http_www.zyh1690.org_opencascade-texture]

[2015-03-07_153525]: http://www.zyh1690.org/wp-content/uploads/2015/03/2015-03-07_153525.jpg
[sampleBottle]: http://www.zyh1690.org/wp-content/uploads/2015/03/sampleBottle1.jpg
[sampleKitchen]: http://www.zyh1690.org/wp-content/uploads/2015/03/sampleKitchen.jpg
[sample]: http://www.zyh1690.org/wp-content/uploads/2015/03/sample.jpg
[http_www.zyh1690.org_opencascade-texture]: http://www.zyh1690.org/opencascade-texture/