Extents3d.md

Extents3d Struct

Overview

The Extents3d struct represents a 3D bounding box defined by minimum and maximum points. It is used for calculating entity bounds, zoom extents, and spatial queries.

Namespace

Autodesk.AutoCAD.Geometry

Key Properties

Property	Type	Description
MinPoint	Point3d	Gets/sets the minimum corner point
MaxPoint	Point3d	Gets/sets the maximum corner point

Key Methods

Method	Return Type	Description
AddPoint(Point3d)	void	Expands extents to include point
AddExtents(Extents3d)	void	Expands extents to include another extents
ExpandBy(Vector3d)	void	Expands extents by vector offset
TransformBy(Matrix3d)	void	Transforms extents by matrix
IsEqualTo(Extents3d)	bool	Checks equality

Code Examples

Example 1: Getting Entity Extents

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    Entity ent = tr.GetObject(entityId, OpenMode.ForRead) as Entity;
    
    // Get entity's bounding box
    Extents3d extents = ent.GeometricExtents;
    
    Point3d min = extents.MinPoint;
    Point3d max = extents.MaxPoint;
    
    // Calculate dimensions
    double width = max.X - min.X;
    double height = max.Y - min.Y;
    double depth = max.Z - min.Z;
    
    ed.WriteMessage($"\nMin: ({min.X:F2}, {min.Y:F2}, {min.Z:F2})");
    ed.WriteMessage($"\nMax: ({max.X:F2}, {max.Y:F2}, {max.Z:F2})");
    ed.WriteMessage($"\nDimensions: {width:F2} x {height:F2} x {depth:F2}");
    
    tr.Commit();
}

Example 2: Combining Multiple Entity Extents

using (Transaction tr = db.TransactionManager.StartTransaction())
{
    BlockTableRecord btr = tr.GetObject(db.CurrentSpaceId, OpenMode.ForRead) as BlockTableRecord;
    
    Extents3d? totalExtents = null;
    
    foreach (ObjectId id in btr)
    {
        Entity ent = tr.GetObject(id, OpenMode.ForRead) as Entity;
        if (ent == null) continue;
        
        try
        {
            Extents3d entExtents = ent.GeometricExtents;
            
            if (totalExtents == null)
                totalExtents = entExtents;
            else
                totalExtents.Value.AddExtents(entExtents);
        }
        catch { }
    }
    
    if (totalExtents != null)
    {
        ed.WriteMessage($"\nTotal extents:");
        ed.WriteMessage($"\n  Min: {totalExtents.Value.MinPoint}");
        ed.WriteMessage($"\n  Max: {totalExtents.Value.MaxPoint}");
    }
    
    tr.Commit();
}

Example 3: Expanding Extents

Point3d min = new Point3d(0, 0, 0);
Point3d max = new Point3d(10, 10, 0);
Extents3d extents = new Extents3d(min, max);

// Add a point (expands if outside current bounds)
Point3d newPoint = new Point3d(15, 5, 0);
extents.AddPoint(newPoint);

ed.WriteMessage($"\nExpanded max: {extents.MaxPoint}"); // (15, 10, 0)

// Expand by offset
Vector3d offset = new Vector3d(1, 1, 1);
extents.ExpandBy(offset);

ed.WriteMessage($"\nAfter expand: Min={extents.MinPoint}, Max={extents.MaxPoint}");

Example 4: Zoom to Extents

[CommandMethod("ZOOMEXTENTS")]
public void ZoomToExtents()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
    
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTableRecord btr = tr.GetObject(db.CurrentSpaceId, OpenMode.ForRead) as BlockTableRecord;
        
        Extents3d? extents = null;
        
        foreach (ObjectId id in btr)
        {
            Entity ent = tr.GetObject(id, OpenMode.ForRead) as Entity;
            if (ent == null) continue;
            
            try
            {
                if (extents == null)
                    extents = ent.GeometricExtents;
                else
                    extents.Value.AddExtents(ent.GeometricExtents);
            }
            catch { }
        }
        
        if (extents != null)
        {
            // Zoom to extents
            Point3d min = extents.Value.MinPoint;
            Point3d max = extents.Value.MaxPoint;
            
            ViewTableRecord view = ed.GetCurrentView();
            view.CenterPoint = new Point2d(
                (min.X + max.X) / 2,
                (min.Y + max.Y) / 2
            );
            
            view.Height = max.Y - min.Y;
            view.Width = max.X - min.X;
            
            ed.SetCurrentView(view);
        }
        
        tr.Commit();
    }
}

Best Practices

1. Null Checks: Check for null when getting entity extents
2. Try-Catch: Some entities may not have valid extents
3. Combining: Use AddExtents() to combine multiple bounding boxes
4. Margins: Use ExpandBy() to add margins around extents

Related Classes

• Point3d - Min/max corner points
• Vector3d - For expanding extents
• Entity - All entities have GeometricExtents property
• Extents2d - 2D bounding box

References

• Autodesk Official Documentation
• Extents3d Struct Reference