Mechanical Modeler

What You Will Learn With This Use Case

An axis system is a feature whose the geometry consists in a vertex (the origin), three edges (three axes) and three planes. There are the sub-elements. This use case is intended to show you how to:

• Retrieve the BRep object [1] associated with one of these sub-elements ,
• Create the BRep feature [1] from this BRep object,
• Create a Sketch based on the BRep feature.

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The CAAMmrAxisSystemBRep Use Case

CAAMmrAxisSystemBRep is a use case of the CAAMechanicalModeler.edu framework that illustrates MechanicalModeler framework capabilities.

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What Does CAAMmrAxisSystemBRep Do

CAAMmrAxisSystemBRep creates an axis system [2], retrieves its XY plane , featurizes it and creates a sketch based on this plane. 

The characteristics of the axis system are the following:

Fig.1: The Axis System Characteristics

The sketch is based on the XY plane, it means in the xz plane of the absolute axis system.

Fig.2: The Sketch Based on the XY Plane 

The above picture is a screen print of the CAAAxisSystemBRep Part document created by the CAAMmrAxisSystemBRep use case. You find it in the CAAMechanicalModeler.edu/InputData directory 

• Unix : InstallRootDirectory/CAAMechanicalModeler.edu/InputData
• Windows : InstallRootDirectory\CAAMechanicalModeler.edu\InputData

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How to Launch CAAMmrAxisSystemBRep

To launch CAAMmrAxisSystemBRep , you will need to set up the build time environment, then compile CAAMmrAxisSystemBRep along with its prerequisites, set up the run time environment, and then execute the use case [3]. To launch the use case execute the command:

mkrun -c CAAMmrAxisSystemBRep [Filename]

where Filename is the complete file name of the output Part document. If no name is given, the Part document, named CAAMmrAxisSystemBRep, is saved in the current directory. 

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Where to Find the CAAMmrAxisSystemBRep Code

The CAAMmrAxisSystemBRep use case is made of one module, CAAMmrAxisSystemBRep.m,  found in the the CAAMechanicalModeler.edu framework and containing a single source program, CAAMmrTestBRep.cpp:

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

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Step-by-Step

There are seven logical steps in CAAMmrAxisSystemBRep:

1. Prolog
2. Retrieves the Factory Interface Pointers
3. Creates an Axis System
4. Retrieves the BRep Plane
5. Features the BRep Plane
6. Creates the Sketch
7. Epilog

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Prolog

CAAMmrAxisSystemBRep begins by creating a session, and creating a new Part document. Next it retrieves the root container of this Part as a pointer to CATIPrtContainer, pIPrtContOnDocument. This is the usual sequence for creating a Part document [4].

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Retrieves the Factory Interface Pointers

There are two factories to retrieve: the axis system and sketch factories. The  CATIMf3DAxisSystemFactory and CATISketchFactory are all the two implemented by the root container, pIPrtContOnDocument the specification container, of the Part document [5].

...
  CATIMf3DAxisSystemFactory * pIMf3DAxisSystemFactoryOnFeatCont = NULL ;
  rc = pIPrtContOnDocument->QueryInterface(IID_CATIMf3DAxisSystemFactory,
                                      (void **) & pIMf3DAxisSystemFactoryOnFeatCont);

  CATISketchFactory * pISketchFactoryOnFeatCont = NULL ;
  rc = pIPrtContOnDocument->QueryInterface(IID_CATISketchFactory,
                                      (void **) & pISketchFactoryOnFeatCont);
...

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Creates an Axis System

An axis system is created thanks to the CATIMf3DAxisSystemFactory interface. pIMf3DAxisSystemFactoryOnFeatCont is the interface pointer on the specification container of the Part document retrieved in the previous section. The article entitled "Creating an Axis System" [2] explains in details the axis system creation. 

Here it is a simple axis system located in (100,0,0) in the absolute axis system and with three axis directions set by mathematical vectors. The first two axis directions, Xdir and Ydir, are given, the third is the vectorial product of the two firsts. NewAxisSystem is consequently an right-handed axis system. 

...
  CATMathPoint Origin (100.0,.0,.0);
  CATMathVector Xdir (1.0,0.0,.0);
  CATMathVector Ydir (0.0,0.0,1.0);

  CATIMf3DAxisSystem_var NewAxisSystem ;
  rc = pIMf3DAxisSystemFactoryOnFeatCont->CreateAxisSystem(Origin,Xdir,Ydir,NewAxisSystem);
 
...

Once the axis system is created, an update is launched to build the geometry.

...
  CATISpecObject * pSpecObjectOnAxisSystem = NULL ;
  rc =NewAxisSystem->QueryInterface(IID_CATISpecObject,(void **)&pSpecObjectOnAxisSystem);

  CATTry
  {
     pSpecObjectOnAxisSystem->Update();
  }
  CATCatch(CATError,error)
  {
     cout<< error->GetNLSMessage().CastToCharPtr() << endl;
     Flush(error);
     return 1 ;
  }
  CATEndTry

  pSpecObjectOnAxisSystem->Release();
  pSpecObjectOnAxisSystem= NULL;
...

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Retrieves the BRep Plane

Once the axis system has been updated, and its geometry computed, it is possible to retrieve one of its sub-element. 

...
  CATIBRepAccess_var PlaneBRep ;
  rc = NewAxisSystem->GetPlaneBRepAccess(CATAxisSystemZNumber,PlaneBRep);
...

The GetPlaneBRepAccess method retrieves a plane of the axis system. The first argument of the method, a CATAxisSystemXYZNumber value, specifies which. With CATAxisSystemZNumber, it is the XY plane, in other words the plane defined by the X and the Y axis directions. 

PlaneBRep is a temporary handler on the plane cell. It is an object of selection [1] usually named a BRep object. The CATIBRepAccess interface manages the BRep objects.

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Featurizes the BRep Plane

To be used as specification, the BRep plane, PlaneBRep, should be featurized. The new feature, MFPlane, is called the BRep feature. The CATIFeaturize interface enables you to do this transformation. The shape of the plane being not important, a featurization with the functional mode is sufficient. Consequently, the FeaturizeF method is used.

...
  CATIFeaturize * pIFeaturizeOnPlane = NULL ;
  rc = PlaneBRep->QueryInterface(IID_CATIFeaturize,(void **) &pIFeaturizeOnPlane);
  ...
  CATISpecObject_var MFPlane = pIFeaturizeOnPlane->FeaturizeF();
...

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Creates the Sketch

The sketch is created thanks to the factory retrieved in the "Retrieves the Factory Interface Pointers" section. MFPlane is the BRep feature support of the sketch. [6]

...
CATISpecObject_var NewSketch = pISketchFactoryOnFeatCont->CreateSketch(MFPlane);
...

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Epilog

The last actions of the use case are the following: save as the Part document, close it and delete the session. It is also described in the Creating a New Document use case [4].

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In Short

This use case explains how to create a sketch based on an axis system's plane.

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References

History

Copyright © 2003, Dassault Systèmes. All rights reserved.