Geometric Modeler

What You Will Learn With This Use Case

The use case creates an attribute an add it to objects. The attribute implementation is defined in the CAAGobAttribute.m module.

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The CAAGobCreation Use Case

CAAGobAttributeCreation is a use case of the CAAGeometricObjects.edu framework that illustrates GeometricObjects framework capabilities.

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What Does CAAGobAttributeCreation Do

This use case creates two PLines. An attribute is added to these geometries.

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How to Launch CAAGobAttributeCreation

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

If you simply type CAAGobAttributeCreation with no argument, the use case executes, but doesn't save the result in an NCGM file. If you want to save this result, provide the full pathname of the NCGM file to create. For example:

With Windows CAAGobCreation e:\AttCreation.NCGM

With UNIX CAAGobCreation /u/AttCreation.NCGM

This NCGM file can be displayed using the CAAGemBrowser use case.

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Where to Find the CAAGobAttributeCreation Code

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

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

The use case uses a class defined in the CAAGobAttribute.m module.

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Step-by-Step

The main program peforms the following steps:

• Creating the Geometry Factory
• Creating the CATPLines
• Retrieving the Attribute Identifier
• Creating the Attribute
• Managing the Attributes
• Managing the References
• Writing the Model and Closing the Container

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Creating the Geometry Factory

The geometry factory (CATGeoFactory) creates and manages all the CATICGMObject (and the curves and surfaces in particular). This creation 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 the CATPLines

A CATPLine is a line in the space of a surface, whatever the surface is. To create a CATPLine, one must specifies the starting and end points: these points are expressed in terms of parameters on the surface. No assumption must be made on the parameterization of the surface. The ways to define a CATSurParameter are:

• Projecting a 3D point on the surface with the geometric operator CATProjectionPtSur
• Using the CATSurface::GetParam method (only for canonical surfaces and a point that is known to be on the surface)
• Using the barycentric constructor, after retrieving the limits (CATSurface::GetLimits) of the surface: this way is illustrated below.

Now, the CATPLines can be created by using the CATGeoFactory::CreatePLine method.

// (c) --- Create a first PLine on piGeoPlane (geometric plane
//
	CATPLine * piPline1 = NULL;
	{
		CATSurParam iStartParam1 ( 0,0 , piGeoPlane->GetParamReference() ) ;
		CATSurParam iEndParam1   ( 0,80, piGeoPlane->GetParamReference() ) ;
		piPline1 = piGeomFactory->CreatePLine(iStartParam1,iEndParam1,piGeoPlane);
		if (NULL==piPline1 ) 
		{
			::CATCloseCGMContainer(piGeomFactory);
			return (1);	
		}
	}

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Retrieving the Attribute Identifier

This operation is done by the CATCGMAttrId::FindAttrId static method which takes as its arguments the attribute name and the logical name of the load module containing the attribute implementation.

Go to the CAAGobAttribute.m module and take a look at the CAAGobAttributeManagement.cpp file which implements the CAAGobAttributeManagement attribute type. The attribute name is the first argument of the CATCGMImplAttribute macro (i.e. CAAGobAttributeManagement) while the CAAGobAT is a string allowing the system to access the load module which contains your implementation.

CATCGMImplAttribute(CAAGobAttributeManagement, CATCGMStreamAttribute, CAAGobAT, 1);

Important:

You must declare the domain name (CAAGobAT) both in the dictionary (CAAGeometricObjects.edu.dico) and in the  AppDef macro. In the present use case, the AppDef declaration is located in a separate file but you could gather all declarations into CAAGobAttributeManagement.cpp. If you need implement several attribute types, you can choose to gather all declarations in the same file as well and use a single AppDef declaration.

// (a) --- Find the attribute identifier
//
const char*  iAttr = "CAAGobAttributeManagement";
const char*  iDomainName = "CAAGobAT";
const CATCGMAttrId* pAttrId = CATCGMAttrId::FindAttrId(iAttr,iDomainName) ;

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Creating the Attribute

This operation can be done in two ways:

• either by using the UAIDPtr macro
• or by using the CreateAttribute static method.

CAAGobAttributeManagement * piAttr1
 =(CAAGobAttributeManagement *) CATCGMAttribute::CreateAttribute(pAttrId); 

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Managing the Attribute

The attribute is assigned a value. The SetValue method is defined in the attribute implementation. Then the attribute is added to each PLines.

// (c) --- Set its value to 2 
//         The SetValue method is defined in the CAAGobAttribute.m module
//
piAttr1->SetValue(2);
  
// (d) --- Add it to the piPline1 and piPline2 CATPlines
//
piPline1->PutAttribute(piAttr1);
piPline2->PutAttribute(piAttr1);

Managing the References

You can cut the reference to an object by using the ReleaseAttribute method applied to the geometry you want to remove the attribute from. In the extract below, at first the number of objects pointed to by the attribute is 2. We check the new number of references after one reference has been cut.

// (e) --- Retrieve the number of references
// 
cout << "Number of objects pointed to by the attribute: (2 expected)";
cout << piAttr1->GetNbAttrRef() << endl;

// (f) --- Release the link between the attribute and piPline2 
// 
piPline2->ReleaseAttribute(piAttr1);

// (g) --- Retrieve the new number of references
// 
cout << "---------------------------------- " << endl;
cout << "After ReleaseAttribute on piPline2 " << endl;
cout << "Number of objects pointed to by the attribute: (1 expected)";
cout << piAttr1->GetNbAttrRef() << endl;

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Writing the Model and Closing the Container

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();
 }	

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

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In Short

The use case illustrates how to create and use CGM attributes.

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References

History

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