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Resetting the origins of block table records in a drawing

—

by

Autodesk Alumni
in

By Gopinath Taget

The following code demonstrates how to modify a block table record’s origin and compensate by moving the insertion point of each of the associated block references.

Please add the function ‘testFunc’ as a command.

void ResetAllInstances(AcDbBlockTableRecord * pBlockTableRecord,

AcGeVector3d &translation)

{

 // Note that this function does not

 // implement any error checking.

 // We are assuming that pBlockTableREcord

 // was opened for write by the calling function

 

 // Iterate through all block references

 // of this block table record.

AcDbBlockReferenceIdIterator * pIterator;

pBlockTableRecord->newBlockReferenceIdIterator(pIterator);

 for (pIterator->start();!pIterator->done();

  pIterator->step())

{

  AcDbBlockReference * pBlockRef;

  pIterator->getBlockReference(pBlockRef,

   AcDb::kForWrite,true);

  // Transform the translation vector from

  // block coordinates to world coordinates.

  AcGeVector3d realTranslation =

   (pBlockRef->blockTransform())*translation;

  // Translate the block reference to

  // counter the effect of the origin change.

  pBlockRef->setPosition(

   pBlockRef->position()+realTranslation);

 

  pBlockRef->close();

} // Next block reference

 delete pIterator;

}

// This is command ‘SGP’

void testFunc()

{

 // Note that error checking is minimal.

ads_name ename ;

ads_point pt ;

 // Ask the user to select an object

 if( acedEntSel (

  L"\nSelect the Block Reference",

  ename, pt) != RTNORM )

  return ;

 // Open it

AcDbObjectId objId;

acdbGetObjectId (objId, ename) ;

AcDbEntity * pEnt;

acdbOpenObject (pEnt, objId, AcDb::kForRead);

 // Check its a block reference

AcDbBlockReference *pRef =

  AcDbBlockReference::cast(pEnt);

 if (pRef == NULL)

{

  pEnt->close();

  return;

}

 // Get the block reference’s

 // associated block table record.

AcDbObjectId blockId =pRef->blockTableRecord ();

pRef->close();

AcDbBlockTableRecord *pBlockTableRecord;

acdbOpenObject (pBlockTableRecord,

  blockId, AcDb::kForWrite);

 // Store the BTR’s current

 // origin (we’ll need it later).

AcGePoint3d origin = pBlockTableRecord->origin();

 // And set its new origin to (0, 0, 0)

pBlockTableRecord->setOrigin(AcGePoint3d(0, 0, 0));

 

 // Create a translation vector for the change

 // in displacement required to offset the

 // origin change (in the block’s coordinate system)

AcGeVector3d translation;

translation.set(-origin[X], -origin[Y], -origin[Z]);

 // Now process all instances of this block

 // reference to compensate for the change in the block origin

ResetAllInstances(pBlockTableRecord, translation);

pBlockTableRecord->close();

}

Comments

6 responses to “Resetting the origins of block table records in a drawing”

  1. Oleg Avatar
    Oleg

    Hi, Gopinath,
    thanks for your article and code
    Here is translation on C#,
    please, let me know if this would works same way:
    public static void ResetAllInstances(BlockTableRecord pBlockTableRecord, Vector3d translation)
    {
    Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
    Editor ed = doc.Editor;
    Database db = doc.Database;
    Transaction tr = doc.TransactionManager.StartTransaction();
    using (tr)
    {
    BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
    string[] blockNames = GetBlockNamesInDrawing(db);
    foreach (string blockName in blockNames)
    {
    ObjectId blkid = bt[blockName];
    BlockTableRecord blkrec = (BlockTableRecord)tr.GetObject(bt[blockName], OpenMode.ForRead);//******************
    ObjectIdCollection ids = blkrec.GetBlockReferenceIds(true, false);
    // Note that this function does not
    // implement any error checking.
    // We are assuming that pBlockTableREcord
    // was opened for write by the calling function
    // Iterate through all block references
    // of this block table record.
    foreach (ObjectId brefid in ids)
    {
    BlockReference bref = (BlockReference)tr.GetObject(brefid, OpenMode.ForWrite);
    // Transform the translation vector from
    // block coordinates to world coordinates.
    Vector3d vec = bref.BlockTransform.Translation;
    Vector3d newvec = vec + translation;
    // Translate the block reference to
    // counter the effect of the origin change.
    bref.Position = bref.Position.TransformBy(Matrix3d.Displacement(newvec));
    }
    }
    tr.Commit();
    }//end using transaction
    }
    // This is command ‘SGP’
    [CommandMethod(“SGP”)]
    public static void testFunc()
    {
    Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
    Editor ed = doc.Editor;
    Database db = doc.Database;
    Transaction tr = doc.TransactionManager.StartTransaction();
    using (tr)
    {
    // Note that error checking is minimal.
    Entity ent;
    // Ask the user to select an object
    PromptEntityOptions peo = new PromptEntityOptions(“\nSelect the Block Reference >>”);
    peo.SetRejectMessage(“\nSelect Block Reference only >>”);
    peo.AddAllowedClass(typeof(BlockReference), false);
    PromptEntityResult res;
    res = ed.GetEntity(peo);
    if (res.Status != PromptStatus.OK)
    return;
    ent = (Entity)tr.GetObject(res.ObjectId, OpenMode.ForRead);
    if (ent == null)
    return;
    BlockReference bref = (BlockReference)ent as BlockReference;
    if (bref != null)
    {
    bref.UpgradeOpen();
    // Get the block reference’s
    // associated block table record.
    ObjectId blockId = bref.BlockTableRecord;
    BlockTableRecord pBlockTableRecord = (BlockTableRecord)tr.GetObject(blockId, OpenMode.ForWrite);
    // Store the BTR’s current
    // origin (we’ll need it later).
    Point3d origin = pBlockTableRecord.Origin;
    // And set its new origin to (10, 20, 0)
    pBlockTableRecord.Origin = new Point3d(10, 20, 0);
    // Create a translation vector for the change
    // in displacement required to offset the
    // origin change (in the block’s coordinate system)
    Vector3d translation = new Vector3d(-origin.X, -origin.Y, -origin.Z);
    // Now process all instances of this block
    // reference to compensate for the change in the block origin
    ResetAllInstances(pBlockTableRecord, translation);
    bref.DowngradeOpen();
    }
    tr.Commit();
    }//end using transaction
    }

    Reply
  2. Gopinath Taget Avatar
    Gopinath Taget

    Hi Oleg,
    Your .NET code is different from the C++ code I provided in a couple of ways. In the testFunc() method, you are setting the block table record origin to a specific value (10, 20, 0) but your translating the block references to (-origin.X, -origin.Y, -origin.Z). This will not give you what you need. You should really be doing this:
    Vector3d translation = new Vector3d(10-origin.X, 20-origin.Y, 0-origin.Z);
    Also, in the ResetAllInstances call, you are iterating through all the block table records which is wrong and unnecessary. You should use the pBlockTableRecord paremeter passed like I did in the C++ code.

    Reply
  3. Oleg Avatar
    Oleg

    Many thanks for your explanation
    I will do it,
    Kind regards,
    Oleg

    Reply
  4. Oleg Avatar
    Oleg

    Hi Gopinath,
    Here is amended code,
    a bit tricky way to iterate through all subentities,
    but seems it’s working good on my end:
    public static void ResetAllInstances(BlockTableRecord pBlockTableRecord, Vector3d translation)
    {
    Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
    Editor ed = doc.Editor;
    Database db = doc.Database;
    Transaction tr = doc.TransactionManager.StartTransaction();
    using (tr)
    {
    // Note that this function does not
    // implement any error checking.
    // We are assuming that pBlockTableREcord
    // was opened for write by the calling function
    // Iterate through all block references
    // of this block table record.
    BlockTableRecordEnumerator pIterator = pBlockTableRecord.GetEnumerator();
    while (pIterator.MoveNext())
    {
    //make sure you’ve work with block instance
    if (pIterator.Current.ObjectClass.IsDerivedFrom(RXClass.GetClass(typeof(BlockReference))) &&
    pIterator.Current.GetType().IsAssignableFrom(typeof(BlockReference)))
    {
    BlockReference pBlockRef = (BlockReference)tr.GetObject(pIterator.Current, OpenMode.ForWrite);
    // Transform the translation vector from
    // block coordinates to world coordinates.
    Vector3d realTranslation = (pBlockRef.BlockTransform) * translation;
    // Translate the block reference to
    // counter the effect of the origin change.
    pBlockRef.Position = pBlockRef.Position + realTranslation;
    }
    } // Next block reference
    pIterator.Dispose();
    tr.Commit();
    }//end using transaction
    }
    // This is command ‘SGP’
    [CommandMethod(“SGP”)]
    public static void testFunc()
    {
    Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
    Editor ed = doc.Editor;
    Database db = doc.Database;
    Transaction tr = doc.TransactionManager.StartTransaction();
    using (tr)
    {
    // Note that error checking is minimal.
    Entity ent;
    // Ask the user to select an object
    PromptEntityOptions peo = new PromptEntityOptions(“\nSelect the Block Reference >>”);
    peo.SetRejectMessage(“\nSelect Block Reference only >>”);
    peo.AddAllowedClass(typeof(BlockReference), false);
    PromptEntityResult res;
    res = ed.GetEntity(peo);
    if (res.Status != PromptStatus.OK)
    return;
    ent = (Entity)tr.GetObject(res.ObjectId, OpenMode.ForRead);
    if (ent == null)
    return;
    BlockReference bref = (BlockReference)ent as BlockReference;
    if (bref != null)
    {
    bref.UpgradeOpen();
    // Get the block reference’s
    // associated block table record.
    ObjectId blockId = bref.BlockTableRecord;
    BlockTableRecord pBlockTableRecord = (BlockTableRecord)tr.GetObject(blockId, OpenMode.ForWrite);
    // Store the BTR’s current
    // origin (we’ll need it later).
    Point3d origin = pBlockTableRecord.Origin;
    // And set its new origin to (10, 20, 0)// dummy point
    pBlockTableRecord.Origin = new Point3d(10, 20, 0);
    // Create a translation vector for the change
    // in displacement required to offset the
    // origin change (in the block’s coordinate system)
    Vector3d translation = new Vector3d(10 – origin.X, 20 – origin.Y, 0 – origin.Z);
    // Now process all instances of this block
    // reference to compensate for the change in the block origin
    ResetAllInstances(pBlockTableRecord, translation);
    bref.DowngradeOpen();
    }
    tr.Commit();
    }//end using transaction
    ed.Regen();// to update origin changes
    }
    Kind regards,
    Oleg

    Reply
  5. Gopinath Taget Avatar
    Gopinath Taget

    Hi Oleg,
    I am surprised this code works. pBlockTableRecord.GetEnumerator(); does not return the block references associated with a block table record. You should really be using pBlockTableRecord.GetBlockReferenceIds to find these block references and change their position.
    Cheers
    Gopinath

    Reply
  6. Ali Avatar
    Ali

    ObjectArx reference says; AcDbBlockTableRecord::origin() will always return (0,0,0) for blocks created by AutoCad versions after release 10.
    So, only setOrigin() changes origin from (0,0,0) by code.
    Origin is not base point as I see in block definition dialog.
    How can I get/set base point instead of origin?

    Reply

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