How to mimic command VPOINT <Rotate> with the .Net API?

By Philippe Leefsma

I’ve got recently a request from a developer who wanted to mimic command VPOINT with option <Rotate> with the possibility of performing a zoom extents at the end. The tricky part is to align the extents with the view direction in order to compute the correct width and height.

Here is the C# code to achieve that:

[CommandMethod("VPointNet")]

public void VPointNet()

{

    Document doc = Application.DocumentManager.MdiActiveDocument;

    Database db = doc.Database;

    Editor ed = doc.Editor;

 

    //Gather inputs: two angles, set zoom to extents or not…

  

    PromptDoubleOptions pdo1 = new PromptDoubleOptions(

        "\nEnter angle in XY plane from X axis (deg): ");

 

    PromptDoubleResult pdr1 = ed.GetDouble(pdo1);

 

    if(pdr1.Status != PromptStatus.OK)

        return;

 

    PromptDoubleOptions
pdo2 = new PromptDoubleOptions(

        "\nEnter angle from XY plane (deg): ");

 

    PromptDoubleResult pdr2 = ed.GetDouble(pdo2);

 

    if(pdr2.Status != PromptStatus.OK)

        return;

 

    PromptKeywordOptions pko = new PromptKeywordOptions(

        "\nZoom Extents?");

 

    pko.AllowNone = false;

    pko.Keywords.Add("Yes");

    pko.Keywords.Add("No");

    pko.Keywords.Default = "Yes";

 

    PromptResult pkr = ed.GetKeywords(pko);

 

    if (pkr.Status != PromptStatus.OK)

     &#
160;  return;

 

    using (Transaction Tx = db.TransactionManager.StartTransaction())

    {

        ViewTable vt = Tx.GetObject(db.ViewTableId, OpenMode.ForRead)

            as ViewTable;

 

        ViewTableRecord newView = ed.GetCurrentView();

 

        newView.ViewDirection = ComputeViewDirection(

            DegToRad(pdr1.Value),

            DegToRad(pdr2.Value));

 

        newView.Name = "VPNetView";

 

        if (pkr.StringResult == "Yes")

        {

            db.UpdateExt(true);

                   

            Extents3d extents = new Extents3d(db.Extmin, db.Extmax);

 

            SetViewToExtents(extents, newView);

        }

  

        if (!vt.Has(newView.Name))

        {

            vt.UpgradeOpen();

 

            vt.Add(newView);

 

            Tx.AddNewlyCreatedDBObject(newView, true);

        }

 

        using (ViewTableRecord vtr = new ViewTableRecord())

        {

            vtr.CopyFrom(newView);

            ed.SetCurrentView(vtr);

        }

 

        Tx.Commit();

    }

}

 

Vector3d ComputeViewDirection(double angleInXyPlane, double angleFromXyPlane)

{

    Vector3d v1 = Vector3d.XAxis.RotateBy(angleInXyPlane, Vector3d.ZAxis);

 

    Vector3d v2 = v1.CrossProduct(Vector3d.ZAxis);

 

    Vector3d viewDir = v1.RotateBy(angleFromXyPlane, v2);

 

    return viewDir;

}

 

void SetViewToExtents(Extents3d extents, AbstractViewTableRecord view)

{

    // Get the screen aspect ratio to calculate the height and width

    double scrRatio = (view.Width / view.Height);

 

    // Prepare Matrix for DCS to WCS transformation

    Matrix3d matWCS2DCS = Matrix3d.PlaneToWorld(view.ViewDirection);

 

    // For DCS target point is the origin

    matWCS2DCS = Matrix3d.Displacement(

        view.Target – Point3d.Origin) * matWCS2DCS;

 

    // WCS Xaxis is twisted by twist angle

    matWCS2DCS = Matrix3d.Rotation(

        -view.ViewTwist,

        view.ViewDirection,

        view.Target) * matWCS2DCS;

 

    matWCS2DCS = matWCS2DCS.Inverse();

 

    // Tranform the extents to the DCS defined by the viewdir

    extents.TransformBy(matWCS2DCS);

 

    // Width of the extents in current view

    double width = (extents.MaxPoint.X – extents.MinPoint.X);

 

    // Height of the extents in current view

    double height = (extents.MaxPoint.Y – extents.MinPoint.Y);

 

    // Get the view center point

    Point2d center = new Point2d(

        (extents.MaxPoint.X + extents.MinPoint.X) * 0.5,

        (extents.MaxPoint.Y + extents.MinPoint.Y) * 0.5);

 

    // Check if the width ‘fits’ in current window

    // if not then get the new height as per

    // the viewports aspect ratio

    if (width > (height * scrRatio))

        height = width / scrRatio;

 

    view.Height = height;

    view.Width = height * scrRatio;

    view.CenterPoint = center;

}

 

double DegToRad(double deg)

{

    return deg * Math.PI / 180.0;

}

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