Manipulate the Current View (.NET)

You access the current view of a viewport in Model or Paper space by using the GetCurrentView method of the Editor object. The GetCurrentView method returns a ViewTableRecord object. You use the ViewTableRecord object to manipulate the magnification, position, and orientation of the view in the active viewport. Once the ViewTableRecord object has been changed, you update the current view of the active viewport with the SetCurrentView method.

Some of the common properties that you will use to manipulate the current view are:

• CenterPoint - Center point of a view in DCS coordinates.
• Height - Height of a view in DCS coordinates. Increase the height to zoom out; decrease the height to zoom in.
• Target - Target of a view in WCS coordinates.
• ViewDirection - Vector from the target to the camera of a view in WCS coordinates.
• ViewTwist - Twist angle in radians of a view.
• Width - Width of a view in DCS coordinates. Increase the width to zoom out; decrease the width to zoom in.

The AutoCAD .NET API does not offer methods to directly manipulate the current view of a drawing. For example, if you want to zoom to the extents of the objects in a drawing or the limits of a drawing, you must manipulate the Width, Height and CenterPoint properties of the current view. To get the extents of limits of a drawing, you use the Extmin, Extmax, Limmin, and Limmax properties of the Database object.

Function used to manipulate the current view

This example code is a common function that is used by later examples. The Zoom function accepts four parameters to accomplish zooming to a boundary, panning or centering the view of a drawing, and scaling the view of a drawing by a given factor. The Zoom procedure expects all coordinate values to be provided in WCS coordinates.

The parameters of the Zoom function are:

• Minimum point - 3D point used to define the lower-left corner of the area to display.
• Maximum point - 3D point used to define the upper-right corner of the area to display.
• Center point - 3D point used to define the center of a view.
• Scale factor - Real number used to specify the scale to increase or decrease the size of a view.

C# Example

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.Geometry;
 
static void Zoom(Point3d pMin, Point3d pMax, Point3d pCenter, double dFactor)
{
    // Get the current document and database
    Document acDoc = Application.DocumentManager.MdiActiveDocument;
    Database acCurDb = acDoc.Database;

    int nCurVport = System.Convert.ToInt32(Application.GetSystemVariable("CVPORT"));

    // Get the extents of the current space when no points 
    // or only a center point is provided
    // Check to see if Model space is current
    if (acCurDb.TileMode == true)
    {
        if (pMin.Equals(new Point3d()) == true && 
            pMax.Equals(new Point3d()) == true)
        {
            pMin = acCurDb.Extmin;
            pMax = acCurDb.Extmax;
        }
    }
    else
    {
        // Check to see if Paper space is current
        if (nCurVport == 1)
        {
            // Get the extents of Paper space
            if (pMin.Equals(new Point3d()) == true && 
                pMax.Equals(new Point3d()) == true)
            {
                pMin = acCurDb.Pextmin;
                pMax = acCurDb.Pextmax;
            }
        }
        else
        {
            // Get the extents of Model space
            if (pMin.Equals(new Point3d()) == true && 
                pMax.Equals(new Point3d()) == true)
            {
                pMin = acCurDb.Extmin;
                pMax = acCurDb.Extmax;
            }
        }
    }

    // Start a transaction
    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Get the current view
        using (ViewTableRecord acView = acDoc.Editor.GetCurrentView())
        {
            Extents3d eExtents;

            // Translate WCS coordinates to DCS
            Matrix3d matWCS2DCS;
            matWCS2DCS = Matrix3d.PlaneToWorld(acView.ViewDirection);
            matWCS2DCS = Matrix3d.Displacement(acView.Target - Point3d.Origin) * matWCS2DCS;
            matWCS2DCS = Matrix3d.Rotation(-acView.ViewTwist, 
                                            acView.ViewDirection, 
                                            acView.Target) * matWCS2DCS;

            // If a center point is specified, define the min and max 
            // point of the extents
            // for Center and Scale modes
            if (pCenter.DistanceTo(Point3d.Origin) != 0)
            {
                pMin = new Point3d(pCenter.X - (acView.Width / 2),
                                    pCenter.Y - (acView.Height / 2), 0);

                pMax = new Point3d((acView.Width / 2) + pCenter.X,
                                    (acView.Height / 2) + pCenter.Y, 0);
            }

            // Create an extents object using a line
            using (Line acLine = new Line(pMin, pMax))
            {
                eExtents = new Extents3d(acLine.Bounds.Value.MinPoint,
                                            acLine.Bounds.Value.MaxPoint);
            }

            // Calculate the ratio between the width and height of the current view
            double dViewRatio;
            dViewRatio = (acView.Width / acView.Height);

            // Tranform the extents of the view
            matWCS2DCS = matWCS2DCS.Inverse();
            eExtents.TransformBy(matWCS2DCS);

            double dWidth;
            double dHeight;
            Point2d pNewCentPt;

            // Check to see if a center point was provided (Center and Scale modes)
            if (pCenter.DistanceTo(Point3d.Origin) != 0)
            {
                dWidth = acView.Width;
                dHeight = acView.Height;

                if (dFactor == 0)
                {
                    pCenter = pCenter.TransformBy(matWCS2DCS);
                }

                pNewCentPt = new Point2d(pCenter.X, pCenter.Y);
            }
            else // Working in Window, Extents and Limits mode
            {
                // Calculate the new width and height of the current view
                dWidth = eExtents.MaxPoint.X - eExtents.MinPoint.X;
                dHeight = eExtents.MaxPoint.Y - eExtents.MinPoint.Y;

                // Get the center of the view
                pNewCentPt = new Point2d(((eExtents.MaxPoint.X + eExtents.MinPoint.X) * 0.5),
                                            ((eExtents.MaxPoint.Y + eExtents.MinPoint.Y) * 0.5));
            }

            // Check to see if the new width fits in current window
            if (dWidth > (dHeight * dViewRatio)) dHeight = dWidth / dViewRatio;

            // Resize and scale the view
            if (dFactor != 0)
            {
                acView.Height = dHeight * dFactor;
                acView.Width = dWidth * dFactor;
            }

            // Set the center of the view
            acView.CenterPoint = pNewCentPt;

            // Set the current view
            acDoc.Editor.SetCurrentView(acView);
        }

        // Commit the changes
        acTrans.Commit();
    }
}