Mechanical Design

What You Will Learn With This Use Case

This use case is intended to help you make your first steps in programming with CATIA Part Design. Its main intent is to fix an element in Part design document. More specifically, you will learn how to:

• Open a part document.
• Access the part feature in the document.
• Access its geometrical features sets, thanks to the CATIDescendants.
• Create Constraint on the one of the children of geometrical features sets.
• List the created constraint.
• Remove the constraint.

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The CAAAuiCreateFixConstraintInPart Use Case

CAAAuiCreateFixConstraintInPart is a use case of the CAAAssemblyUI.edu framework that illustrates the ConstraintModeler framework capabilities.

Before discussing the use case, some main concepts, about the fix constraint, have to be introduced:

• A fix constraint is a geometrical relation created on a feature or a body, with respect to the 3D space

• The object then cannot be moved in 3D space, though its defining parameters can be modified

• The fix constraint appears in the specification tree at the same level as the element to be constrained and they are displayed under PartBody or GeometricalSet, which owns the element.

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What Does CAAAuiCreateFixConstraintInPart Do

CAAAuiCreateFixConstraintInPart:

• Opens a session.
• Opens a document.
• Gets the root (spec) container of given CATPart.
• Gets the mechanicalPart feature which is contained in the specification container of a Part document.
• Retrieves all (non order) GeometricalSet type children of a Part.
• Get the (line) child by its (3rd) position of GeometricalSet.
• Create a constraint : Type - Fix constraint, Element to be constrained - Line.
• Get the list of constraints under a given Part.
• Remove constraint.
• Closes document.
• Closes session.

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How to Launch CAAAuiCreateFixConstraintInPart

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

Launch the use case as follows:

• With Windows

  e:>CAAAuiCreateFixConstraintInPart InputDirectory OutputDirectory

• With UNIX

  $ CAAAuiCreateFixConstraintInPart InputDirectory OutputDirectory

where:

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Where to Find the CAAAuiCreateFixConstraintInPart Code

The CAAAuiCreateFixConstraintInPart use case is located in the CAAAuiCreateFixConstraintInPart.m module of the CAAAssemblyUI.edu framework:

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

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Replaying CAAAuiCreateFixConstraintInPart ODT

The required data for CAAAuiCreateFixConstraintInPart ODT is located in the CAAAssemblyUI.tst framework:

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

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Step-by-Step

There are five main steps in CAAAuiCreateFixConstraintInPart:

1. Prolog
2. Creating a fix constraint in part document
3. Listing the constraint
4. Removing the Constraint
5. Epilog

We will now comment each of those sections by looking the code.

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Prolog

CAAAuiCreateFixConstraintInPart begins by checking that the command lines contains one argument (file path of CATPart document). It then creates a session, and opens a CATPart document with the help static method OpenDocument of class CATProductDocument. It then retrieves the document's root(specification) container handle of type CATIPrtContainer, and then retrieves mechanical part feature handle (of type CATIPrtPart). It searches part's descendants (CATIDescendants) of type "non-ordered geometrical set". Under geometrical set, it searches for the 3rd child that is line and retrieves line's handle ( of type CATISpecObject) as

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Creating a fix constraint in part document.

  ...
CATICst_var spCst = NULL_var;
CATLISTV(CATBaseUnknown_var) ElemList; 
ElemList.Append(spSpecLine);

// Create a constraint : Type - Fix constraint, Element to be constrained - Line,  
rc = CATConstraintServices::CreateConstraintIn(	spPart, 
						CstType_Reference,
						ElemList,
						0.0,
						CATCstVal_Mode_Constrained,
						spCst);

// Process errors
  ...

The constraint is created using the static method CreateConstraintIn of the class CATConstraintServices. The only out argument to this method is the handle of the created constraint. CreateConstraintIn has the following arguments...

Listing the constraint.

  ...
// Get the list of constraints under a given Part 
CATLISTV(CATICst_var) CstList;
rc=CATConstraintServices::ListConstraints(spPart, CstList);
if(SUCCEEDED(rc))
{
	cout << "***** Listing constraints *****" << endl;
	cout << "*** Total constraints = " << CstList.Size() << endl;
}
else
{
	// Process errors
}
  ...

The constraints are listed using the static method ListConstraints of the class CATConstraintServices. If no constraints are found, the call to method will fail. ListConstraints has the following arguments...

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Removing the Constraint.

  ...
// Remove constraints
rc = CATConstraintServices::RemoveConstraint(spCst);
if ( SUCCEEDED(rc) )
	cout << "***** Removing constraint ***** " << endl;
else
{
	// Process errors
}
  ...

The constraint is removed using the static method RemoveConstraint of the class CATConstraintServices. RemoveConstraint has the following arguments...

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Epilog

Close the document an then session is closed, as usual.

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In Short

This use case has demonstrated the way to create, list and remove the fix constraint on the (non-order geometrical set) element of a part design document.

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References

History

Copyright © 2005, Dassault Systèmes. All rights reserved.