Geometric Modeler

What You Will Learn With This Use Case

In this use case, you learn how to compute the area of a face as well as the length of an edge.

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The CAATopProperties Use Case

CAATopProperties is a use case of the CAATopologicalOperators.edu framework that illustrates TopologicalOperators framework capabilities.

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What Does CAATopProperties Do?

This use case:

1. creates the geometric factory
2. creates a solid sphere
3. computes the area of each face
4. computes the length of each edge
5. writes the model and closes the container.

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How to Launch CAATopProperties

To launch CAATopProperties, you will need to set up the build time environment, then compile CAATopProperties.m along with its prerequisites, set up the run time environment, and then execute the use case [1].

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Where to Find the CAATopProperties Code

The CAATopProperties use case is made of a main named CAATopProperties.cpp located in the CAATopProperties.m module of the CAATopologicalOperators.edu framework:

where InstallRootDirectory is the directory where the CAA CD-ROM is installed.

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Step-by-Step

The program:

1. Creates the Geometry Factory
2. Creates the sphere (CATSolidSphere)
3. Computes the area of each face
4. Computes the length of each edge
5. Writes the Model and Closes the Container

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Creating the Geometry Factory

The geometry factory (CATGeoFactory) creates and manages all the CATICGMObject : it creates the points, curves, surfaces and bodies and remove them.

The CATGeoFactory creation itself is done by the global function ::CATCreateCGMContainer.

Notice that the factory can be defined by reading a NCGM file that was previously stored. In that case, the global function ::CATLoadCGMContainer must be used.

CATGeoFactory* piGeomFactory = ::CATCreateCGMContainer() ;
if (NULL==piGeomFactory) return (1);

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Creating a sphere

CATMathPoint p1(0,0,0);  // the sphere center
 
CATSolidSphere * pSphereOpe = ::CATCreateSolidSphere(piGeomFactory, 
     &topdata,
     p1,
     100.0); // the radius
...   
pSphereOpe -> Run();
CATBody * pBodySphere = pSphereOpe -> GetResult();
...

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Computing the area of a CATFace

To retrieve a face area, you must:

• use the CATDynCreateMassProperties3D function and pass as its argument the face whose area is to be calculated
• apply the GetWetArea method to the returned CATDynMassProperties3D.

for (int i=1;(i <= nbFaces)  ;i++) 
 {
     CATFace * pFace = (CATFace *)listFaces[i];
     CATDynMassProperties3D * pDynMassOpe0 = 
         CATDynCreateMassProperties3D(pFace ) ;
     if (NULL == pDynMassOpe0)
     {
      ::CATCloseCGMContainer(piGeomFactory);
       return (1);
     }	
     // Expected area 4*PI*(R**2)/4
     cout << "Face " << i << " area: " << pDynMassOpe0->GetWetArea() << endl;
     delete pDynMassOpe0; pDynMassOpe0=NULL;
 }

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Computing the length of a CATEdge

To retrieve a face area, you must:

• use the CATDynCreateMassProperties3D function and pass as its argument the edge whose length is to be calculated
• apply the GetLength method to the returned CATDynMassProperties3D.

for (i=1;(i <= nbEdges)  ;i++) 
 {
     CATEdge * pEdge = (CATEdge *)listEdges[i];
     if (pEdge == NULL) return 1;
     CATDynMassProperties3D * pDynMassOpe1 = 
         CATDynCreateMassProperties3D(pEdge ) ;
     if (NULL == pDynMassOpe1)
     {
         ::CATCloseCGMContainer(piGeomFactory);
         return (1);
     }	
     
     cout << "Edge " << i << " length: " << pDynMassOpe1->GetLength() << endl;
     cout << pEdge->GetPersistentTag() << endl;
     delete pDynMassOpe1; pDynMassOpe1=NULL;
 }

This is the length with is displayed on the standard output:

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Writing the Model and Closing the Factory

Before ending, we must first release the software configuration.

// Releases the configuration
    pConfig->Release();

To save the model in a file, the ::CATSaveCGMContainer global function is used. Notice that in the use case, the save is conditioned by an input parameter representing the file inside which the model must be saved.

The use case ends with the closure of the geometry factory, done by the ::CATCloseCGMContainer global function.

 if(1==toStore)
 {
#ifdef _WINDOWS_SOURCE
   ofstream filetowrite(pfileName, ios::binary ) ;
#else
   ofstream filetowrite(pfileName,ios::out,filebuf::openprot) ;
#endif

   ::CATSaveCGMContainer(piGeomFactory,filetowrite);
   filetowrite.close();
 }	

 //
 // Close the container
 //
	
 ::CATCloseCGMContainer(piGeomFactory);

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In Short

This use case explains how to compute the area of a face and the length of an edge by using the CATDynMassProperties3D class.

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References

History

Copyright © 2002, Dassault Systèmes. All rights reserved.