Geometric Modeler

Operators to Copy or Move Objects

CATCloneManager is a class representing an operator that manages the copy and paste of a set of objects implementing the CATICGMObject interface, that is to say the persistent objects provided by the CGM offering. This operation, that also takes into account the forward linked object, is called a cloning, and is especially useful to design your own cut, copy, paste applications.

Why is there a specific class for this process, instead of a method in each class of each geometric object? This could be the easiest way to do when the objects to clone are isolated, that is, have no links with other objects. But take now two curves C1 and C2 laying on the same surface. You want to globally copy the set of the three objects C1, C2 and the underlying surface. If the copy process was at the geometric object level, the surface would be twice copied, and the resulting objects would not represent an exact image of the global initial set.

To prevent from this kind of configuration, the cloning process has a global knowledge of the objects to clone. Therefore, the role of the CATCloneManager is to federate the way to copy and paste objects and their forward linked objects. In particular, the manager clones a list of selected objects, without unnecessarily duplicating the forward common linked objects.

The same frame occurs for the transformation of geometric objects implementing the CATGeometry interface. For these objects that have a geometric meaning, the geometric transformation process follows the same way than the clone process. Hence, an object implementing the CATGeometry interface, which is a kind of CATICGMObject interface, will be geometrically transformed, with or without duplication, by the mean of a CATTransfoManager instance, which is a kind of CATCloneManager instance.

Fig1: Inheritance between CATCloneManager and CATTransfoManager

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The CATCloneManager

The programmer gives to the CATCloneManager the objects to be cloned together, by calling the CATCloneManager::Add method. All the objects must belong to the same container (a container is an object containing other objects) to be processed in a single operation.

The copy and paste is not made at the creation of the clone process, or when objects are added to the list to copy, but triggered by the CATCloneManager:Run method.

After the run, you can retrieve the cloned object corresponding to each object of the input list.

If there are topological objects to clone (topological objects are kind of geometric objects), the CATCloneManager creates, under request, the topological journal associated with the cloning operation.

The CATCloneManager instances are transient, and therefore cannot be streamed.

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Two Modes of Cloning

The cloning process can be done as a single copy or a full copy. This mode is ruled by the CATCloneManagerType:

CatCGMSingleDuplicate

Only copies and pastes the objects that are Added to the CATCloneManager. This is only available if the objects are copied from and pasted in the same container

CatCGMFullDuplicate

Copies and pastes the objects that are Added to the CATCloneManager and their forward linked objects.

Fig2: Behavior of the duplication according to the CATCloneManagerType

These diagrams show the behavior of the CATCloneManager for each mode: C1 and C2 are two curves laying on the same Surface. Then, C1 and C2 have Surface as forward linked object. When C2 is selected in SingleDuplicate, its copy C2_c lays on Surface. In FullDuplicate, Surface is also duplicated in Surface_c When C1 and C2 are selected in SingleDuplicate, their copies C1_c and C2_c respectively lay on Surface. In FullDuplicate, their copies lay on Surface_c, the copy of Surface, that has been duplicated only once.

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A Code Sample

The following example illustrates how to copy the two curves C1 and C1 of the previous section and paste them into an other container. The result will be two new curves laying on the same new surface, with the same characteristics as the initial one.

CATCloneManager MyManager(GeoFactoryForPasting); // the CATGeoFactory is also a container
MyManager.Add(C1);   
MyManager.Add(C2);
// Copies C1 and C2 and paste them in GeoFactoryForPasting
MyManager.Run();  
// Retrieves the copy of C1  
CATICGMObject* ClonedObject=MyManager.ReadImage(C1);

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How a CATICGMObject and a CATCloneManager Cooperate

The CATCloneManager globally manages the cloning, but delegates the copy of a single object to each object.

1. The CATCloneManager asks the object to clone itself through the CATICGMObject::Clone method.
2. The object to clone asks back the CATCloneManager for the copy of its forward linked objects through the CATCloneManager::ComputeImage method.
   • If the copy of the forward linked object has already been created during the cloning process, it is directly returned
   • Otherwise, the process re-runs at the step 1 for the linked object.

Hence, there are two types of methods of a CATCloneManager

• "user methods", that you call to clone CATICGMObjects, as in the code sample :

  Add

  Adds objects of the same container to the set of objects to clone

  Run

  Triggers the cloning process

  ReadImage

  Retrieves a pasted object

  WriteReport

  Writes topological items in the journal

  GetFactory

  Retrieves the factory of the pasted objects

• "object methods", to use for writing the Clone method of a new class of CATICGMObject . These methods are not seen by the CAA programmer.

  ComputeImage

  Called inside the code of a CATICGMObject.

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The CATTransfoManager

This operator is a kind of CATCloneManager, that moves CATGeometry objects, with or without copying them. This part highlights the new properties and behaviors with respect to those inherited from CATCloneManager.

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Inherited Properties

The global architecture is of course inherited. It includes:

• The cooperation between the manager ant the objects it manages
• The behavior of "users" and "objects" methods that have already been described
• The fact that it cannot be streamed.

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New Properties

• The first new property is obviously the transformation. The CATTransfoManager takes two types of transformations:
  • Linear transformations, instances of CATMathTransformation, representing a simple displacement of the object. These linear transformations must be invertible.
  • Non linear transformations, instances of CATMathNonLinearTransformation, which definition depends on the point where the transformation is done. This is useful for describing deformations such as sheet metal folding and unfolding.
• Now, the CatCGMSingleDuplicate/FullDuplicate mode has no more meaning for transformations. It is replaced by the CATTransfoManagerType, defined as follows:

CATTransfoManager::Replace

Transforms the objects that are Added to the CATransfoManager and their forward linked objects that are not geometrically invariant. In some cases, a copy occurs, when a pointing object is not in the selection. Do not use this mode for the transformation of topological objects, because of the smart mechanism. For your reminder, a topological object is a kind of geometric object with logical boundaries and the smart mechanism is the fact that topological objects to modify have first to be duplicated.

CATTransfoManager::Duplicate

Copies, transforms and pastes objects that are Added to the CATransfoManager and their forward linked objects that are not geometrically invariant, without unnecessarily duplicating common forward linked objects. In particular, a CATTransfoManager with this option and the identity transformation gives the same result as a CATCloneManager with CatCGMSingleDuplicate mode.

CATTransfoManager::FullDuplicate

Duplicates and transforms the objects that are Added to the CATTransfoManager. Duplicates a forward linked object even if it is geometrically invariant by the transformation,

The rules for the duplication of the forward linked objects in the same container are as follows:

• If a forward linked object is geometrically invariant by the transformation, this object is not duplicated, except if this forward linked object is specifically Added to the CATTransfoManager. Invariant means that the transformation does not change the object with regards to its maximum limits: for example, a line is invariant by a transformation along its direction, a circle is invariant by a rotation around an axis perpendicular to its plane and passing by its center.
• Any forward linked object that is not geometrically invariant is copied or replaced

The following figures illustrate the behavior of the CATTransfoManager in different cases:

Note

The specific methods of a CATTransfoManager are

• "user methods", that you call to transform CATGeometry objects:

  GetMathTransformation

  Retrieves the transformation

  GetMathNonLinearTransformation

  Retrieves the non linear transformation

  RetrieveTransfoW

  Retrieves the 1D transformation to apply to an object that lays to another object that is geometrically invariant along one direction.

• "object methods", to use for writing the Move3D and CloneAndMove3D methods of a new class of CATGeometry you want to create: Compute, ComputeW, ComputeUV, SetTransfoW, SetTransfoUV, IsIdentity, IsSimilitide, GetOrientationChange, IsInvariant that are called inside the code of a CATGeometry. These methods are not seen by the CAA programmer.

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In Short

• The CATCloneManager is an operator that copies and pastes a set of CATICGMObject, and their forward linked objects if needed.
• The CATTransfoManager is a kind of CATCloneManager that also moves set of CATGeometry objects.
• These operators cooperate with the objects for more efficiency.

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References

History

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